There’s a lot of inaccurate and out of date information out there. Some of it is propaganda but most is a combination of misunderstanding and patient forum myth spreading …….
Myth 1: All Neuroendocrine Tumours are benign
Not true. By any scientific definition, the word ‘tumour’ means ‘an abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Tumours may be benign (not cancerous), or malignant (cancerous)’. Sure, some NETs will be benign. However, The World Health Organisation (WHO) 2010 classification for digestive system is based on the concept that all NETs have malignant potential, and has therefore abandoned the division into benign and malignant NETs and tumours of uncertain malignant potential. This has been reinforced in the 2017 update to include clarification for other endocrine organ types of NET including Pheochromocytoma. Read more here. The word ‘Carcinoid’ is inextricably linked with this issue – read here why we need to stop using the term to help fight the benign myth.
Myth 2: Neuroendocrine Tumours is a terminal condition
Not true. By any definition of the word terminal in a medical diagnostic context, most NET patients have a good prognostic outlook, even those with metastatic and incurable variants of the disease. Read more here.
Myth 3: Carcinoid is another word for Neuroendocrine Tumours
Not true. Carcinoid is a very old term and was phased out years ago. Carcinoid is not mentioned in the latest WHO Classification schemes for Neuroendocrine Neoplasms (a term covering Neuroendocrine Tumours and Neuroendocrine Carcinoma). Unfortunately, the problem is exacerbated by organisations and individuals who still use the word. Also, those who use the following terms:
“Carcinoid and Neuroendocrine”,
“Neuroendocrine and Carcinoid”,
“Carcinoid NETs” or “CNET”
These are all contextually incorrect and misleading terms (not to mention the bad grammar). ENETS, NANETS and NCCN publications are gradually phasing the word out except in relation to Carcinoid Syndrome (and even then there could be easy solutions for this). Read more here and here.
Myth 4: All NET patients get ‘carcinoid syndrome’
Not true. Firstly, many NET cancers are non-functional; and secondly, carcinoid syndrome is only one of a number of “NET Syndromes” associated with the various types of NET. However, the issue is further confused by those who use the word ‘Carcinoid‘ to incorrectly refer to all NETs and use Carcinoid Syndrome to refer to all NET Syndromes. Read more here.
Not true. Steve Jobs had a Neuroendocrine Tumour of the Pancreas. Ditto for a few other famous names. Read more here.
Myth 7: I’m not getting chemotherapy, I must be doing OK?
Not true. For some cancers or some sub-types of cancers, although it remains an option, chemotherapy is not particularly effective, e.g. some types of Neuroendocrine Cancer (NETs). In general, well differentiated NETs do not normally show a high degree of sensitivity to chemotherapy, although some primary locations fare better than others. However, many of the treatments for NET Cancer are somewhat harsh, have long-term consequences, and have no visible effects. NET patients are often said to “look well” but that doesn’t mean they are not struggling behind the scenes or under the surface. Read more here. P.S. Afinitor (Everolimus), Sutent (Sunitinib) are not chemo – Read more here.
Myth 8: All diarrhea is caused by carcinoid syndrome
Not true. It could be one of the other syndromes or tumor types or a side effect of your treatment. Check out this post.
Myth 9: Neuroendocrine Tumours is a ‘good cancer’
Not true. Simply, no cancer is good. Some are statistically worse than others in prognostic terms, that’s true…… but living with NETs is very often not a walk in the park. However, no one cancer is better to get than any other – they’re all bad. Read more here.
Myth 10: Every NET Patient was misdiagnosed for years
Not true. Many NET Patients are correctly diagnosed early on in their investigation and in a reasonable time. This myth is perpetuated because of two things: firstly, on forums, the ratio of long-term misdiagnosis is high creating a false perception; and secondly, the method of capturing patient surveys is not extensive enough – again creating a false perception. In fact, the latest and largest database analysis from US indicates earlier diagnosis is improving, with more and more NETs being picked up at an early stage. Read more here.
Myth 11: Somatostatin Analogues are a type of Chemotherapy
Not true. Somatostatin Analogues (e.g. Octreotide and Lanreotide) are not chemotherapy, they are hormone inhibiting drugs. They are more biotherapy. As the drugs latch onto somatostatin receptors, they are more targeted than systemic. For the record, Everolimus (Afinitor) and Sunitinib (Sutent) are not chemotherapy either. Read more here.
Myth 12: Stuart Scott (ESPN) and Audrey Hepburn had Neuroendocrine Cancer.
Not true. This is a common misunderstanding within the community. They both had Pseudomyxoma Peritonei (PMP). Read more about PMP here.
Myth 13: I’ve been diagnosed with Neuroendocrine Tumours – my life is over
Not true. Many patients live a very long time and lead fairly normal lives with the right treatment and support. It’s difficult but I try not to use ‘I can’t’ too much. Read more here.
Myth 14: There are only a handful of Neuroendocrine specialists in the world
Not true. There are many specialists in many countries. Get links to specialists by clicking here.
Myth 15: The Ga68 PET scan is replacing the CT and MRI scan in routine surveillance for all NET Patients
Not true. It is actually replacing the Octreotide Scan for particular purposes, or will eventually. Read more by clicking here.
Myth 16: All NET Patients are Zebras
Not true. They are in fact human beings and we should treat them as such. Please don’t call me a zebra and please don’t use the term on my social media sites, I refuse to perpetuate this outdated dogma.
Myth 17: Multiple Endocrine Neoplasia (MEN) is a type of Neuroendocrine Tumour
Not true. Multiple Endocrine Neoplasia are syndromes and inherited disorders. You can have MEN and not have any tumours. However, these disorders can put people at more risk of developing Neuroendocrine or Endocrine Tumours. Read morehere
Myth 18: Palliative Care means end of life or hospice care
Not true. Palliative care is specialized medical care that focuses on providing patients relief from pain and other symptoms of a serious illness. A multidisciplinary care team aims to improve quality of life for people who have serious or life-threatening illnesses, no matter the diagnosis or stage of disease. Read more here
Myth 19: Serotonin is found in foods
Not true. Serotonin is manufactured in the body. Read more here
Myth 20: NETs cannot be cured
Not true. If caught early enough, some NETs can be treated with curative intent (totally resected) with little or no further follow up. It says this in ENETS and NANETS publications which are authored by our top specialists. If we can’t believe them, who can we believe? Read more here.
Myth 21: Pancreatic Enzyme Replacement Therapy (Creon etc) is only for pancreatic patients
Not true. It’s for any patient who is exhibiting exocrine pancreatic insufficiency. Read more here.
More to follow no doubt
For general cancer myths and the dangers of fake health news, please see my ARTICLE HERE
Thanks for reading
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5 years ago today, I had a bunch of lymph nodes removed. Two separate areas were resected, only one was showing growth but both were showing up as hotspots on an Octreoscan. I had known since shortly after diagnosis in 2010 that ‘hotspots’ were showing in my left ‘axillary’ lymph nodes (armpit) and my left ‘supraclavicular fossa’ (SCF) lymph nodes (clavicle area). Some 10 months previously, I had a major liver resectionand 5 months prior to the liver resection, I had a small intestinal primary removedincluding work on some associated complications. There had always been a plan to optimise cytoreduction of my distant metastases, it was just a matter of timing. I still can’t get my head round why metastases from a small intestinal NET managed to get to this area but not others!
Distant nodal metastasis treatment
A total of 9 nodes were removed from my left armpit (a very common operation for breast cancer patients). The surgeon had inspected the area and found some were palpable and my normally stable Chromogranin Amarker was showing a small spike out of range. During the same operation under general anaesthetic, an ultrasound directed SCF nodal ‘exploration’ was carried out. When biopsied, 5 of the 9 resected axillary nodes were tested positive (Ki-67 <5) but the 5 SCF nodes removed were tested negative. The subsequent Octreoscan still lit up in the left SCF area but the lights on the left axillary area were ‘extinguished’. There is no pathological enlargement or pain in the left SCF area – so this is just monitored.
Apart from a very faint scar in the left SCF area, there does not appear to be any side effects from this exploratory surgery. The left axillary area cut is well hidden by hair growth but I do sense a lack of feeling in the area. Additionally, I have a very mild case of lymphedema in my left hand which occasionally looks slightly swollen – the consequences of cancerand its treatment. Fluid build-up, or post-operative seroma, can be a side effect of a lymphadenectomy. In fact, within a month of the operation, I had to have circa 160mls of fluid removed on 4 occasions from my armpit. It was uncomfortable and painful, resulting in additional time off work. The surgeon used a fine needle aspiration to draw out the fluid, a painless procedure. It eventually cleared up and everything was back to normal. The specialist said my left arm would be slightly more susceptible to infections and suggested to avoid using my left arm for blood draws and other invasive procedures and injuries.
Other close calls (“to cut or not to cut”)
I have a 19mm thyroid lesion which was pointed out to me in 2013. This has been biopsied with inconclusive results. Although the thyroid is an endocrine gland, it looks like a non-NET problem so far. Thyroid nodules are in fact very common and statistically, 50-70% of all 50-70 year olds will have at least one nodule present (i.e. if you are in your 50s, there is a 50% chance you will have one nodule and so on). The vast majority will never bother a person while they live. I attend an annual Endocrine MDT where this is monitored in close coordination with the NET MDT. It’s actually managed by the same surgeon who carried out the nodal work above.
I have a 3mm lung nodule, discovered in 2011. Apparently, lung nodules are a pretty common incidental finding with 1 per 500 X-rays and 1 per 100 CT scans finding them. This is monitored and hasn’t changed since noted.
Theranostics is a joining of the words therapeutics and diagnostics. You may also see it conveyed as ‘Theragnostics’ and these terms are interchangeable. The basic aim of theranotistics is to find and then destroy the ‘bad guys‘. With Neuroendocrine Cancer, finding the tumours (the bad guys) can often be a challenge – they can be small and/or difficult to find – they are sometimes expert at camouflage. Moreover, once found, they can then be difficult to treat (destroy), as they can often prove resistant to conventional cancer drugs and many are inoperable due to sheer quantity, spread and positioning. When they are found and identified, it’s also really helpful to know from the intelligence gathered, how successful the destroy (therapeutic) part of the mission might be.
The nuclear scan uses the same nuclear material as the therapy, therefore if you cancer lights up on the nuclear scan, then the therapy will find its way to the cancer and hopefully work well. That is the beauty of theranostic pairing, i.e. the use of the same agent in the diagnostics – the ability to find, estimate likely success criteria and then hopefully destroy – or at least reduce the capability of the tumours and extend life.
A great example of an approved Theranostic Pairin Neuroendocrine Cancer, is the combination of the Somatostatin Receptor based Ga68 PET scan using NETSPOT or SomaKit TOC™ (US/Europe respectively) and Peptide Receptor Radiotherapy (PRRT) using Lutathera which both target NETs expressing the same somatostatin receptor, with PRRT intended to kill tumor cells by emitting a different kind of low-energy, short-range radiation than that of the diagnostic version. As mentioned above, the Ga68 PET scan can give a reasonably indication of therapeutic success using PRRT based on measurements taken during the scan (too complex for this article).
Nuclear medicine makes it possible by using the same molecular targeting compound to create diagnostic and therapeutic drugs, which work as theranostic pairings. Advanced Accelerator Applications’ theranostic platform is based on radiolabelling a single targeting molecule with either gallium Ga-68 for diagnostic use or lutetium Lu-177 for therapeutic use. AAA’s pipeline now includes several theranostic drug pairings for oncology indications including prostate and breast cancer; and gastrointestinal stromal tumors (GIST).
THERANOSTICS – FIND
Newer imaging agents targeting somatostatin receptors (SSTR) labelled with 68 Ga have been developed, namely, DOTATATE, DOTATOC and DOTANOC. They are collectively referred to as SSTR PET.
The main difference among these three tracers (DOTA-TOC, DOTA-NOC, and DOTA-TATE) is their variable affinity to SSTR subtypes. All of them can bind to SSTR2 and SSTR5, while only DOTA-NOC shows good affinity for SSTR3.
These agents have several benefits over In111-pentetreotide (Octreotide scan), including improved detection sensitivity, improved patient convenience due to the 2 hour length of the study (compared to 2 or 3 days with Octreoscan), decreased radiation dose, decreased biliary excretion due to earlier imaging after radiotracer administration, and the ability to quantify uptake. The quantification of the uptake can help decide whether a patient is suitable for PRRT. Eventually, all Octreotide scans should be replaced with SSTR PET. To confirm the advantages of SSTR PET over Octreotide scans, a study comprising 1,561 patients reported a change in tumour management occurred in over a third of patients after SSTR PET/CT even when performed after an Octreotide scan. Worth pointing out that SSTR PET is replacing the ageing Octreotide scan and not conventional imaging (CI). You can see the recommended scenarios for use of SSTR PET in this article published by the Journal of Nuclear Medicine
Ga68 PET scans have been in many locations for some time. Current excitement is focused on USA locations with Ga68 PET (NETSPOT) only recently approved (DOTATATE). Other countries/scan centres may use one of the other types of imaging agent.
Read much more about this scan in my detailed article on Ga68 PET here.
So SSTR PETs above have the ability to find and estimate likely success criteria for therapy. We are now in a position to move on to ‘THERApy’ – e.g. Peptide Receptor Radiotherapy or PRRT.
THERANOSTICS – DESTROY
Lutathera® (note the ‘THERA’ which makes up the brand name)
Europe Approval: LUTATHERA®(lutetium (177Lu) Oxodotreotide) is indicated for the treatment of unresectable or metastatic, progressive, well differentiated (G1 and G2), somatostatin receptor positive gastroenteropancreatic neuroendocrine tumours (GEPNETs) in adults.
USA Approval: LUTATHERA® (lutetium Lu 177 dotatate) is indicated for the treatment of somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumors (GEP-NETs), including foregut, midgut and hindgut neuroendocrine tumors in adults.
For commercial purposes, the drug may be slightly different on a regional basis. For all intents and purposes it does the same job.
PRRT with LUTATHERA®
LUTATHERA® solution for infusion is a ‘radiolabelled somatostatin analog (SSA)’ comprised of a radionuclide (Lutetium-177) and a peptide (differs between Europe and USA)
The relevant SSA binds with high affinity to the somatostatin receptors (SSTR) overexpressed in malignant neuroendocrine cells such as the ones found in GEP-NETs.
Lutetium-177 is a β particle emitting radionuclide, with a mean penetration range of 0.67 millimetres in tissue (maximum penetration range of 2.2 mm) which is sufficient to kill targeted tumour cells with a limited effect on neighbouring normal cells.
The affinity for SSTRs and the specificity of binding ensures a high level of specificity in the delivery of radiation to the tumour. Before starting treatment with LUTATHERA®, imaging must confirm the presence of these receptors in tumour tissues.
As an example of how the drug is administered, please watch this short video from the European site:
Please see the following post for a summary of PRRT activity worldwide. Please note this linked article is not designed to contain a list of every single location or country available – please bear that in mind when you read it – CLICK HERE
A fairly common disposition of metastatic Neuroendocrine Tumours (NETs) is a primary with associated local/regional secondary’s (e.g. lymph nodes, mesentery and others) with liver metastases. Technically speaking, the liver is distant. However, many metastatic patients have additional and odd appearances in even more distant places, including (but not limited to) the extremities and the head & neck. In certain NETs, these might be an additional primary (e.g. in the case of Multiple Endocrine Neoplasia (MEN); or they could even be a totally different cancer. The worry with NETs is that the ‘little suckers‘ can sometimes make these surprise appearances given that neuroendocrine cells are everywhere.
Cancer doesn’t just spread through the blood steam, it can also spread through the lymphatic system. This is a system of thin tubes (vessels) and lymph nodes that run throughout the body in the same way blood vessels do. The lymph system is an important part of our immune system as it plays a role in fighting bacteria and other infections; and destroying old or abnormal cells, such as cancer cells. The lymphatic system also contains organs, some of which feature regularly in NETs. If cancer cells go into the small lymph vessels close to the primary tumour they can be carried into nearby lymph glands where they stick around. In the lymph glands they may be destroyed (that is actually one of the jobs of the lymph glands) but some may survive and grow to form tumours in one or more lymph nodes.
I also had the usual bulky chains of lymph node metastases in or around the mesentery that frequently appear with an abdominal primary (in my case the small intestine). These were all removed as part of my primary resection. However, I knew since shortly after diagnosis in 2010 that I had ‘hotspots’ in my left ‘axillary’ lymph nodes (armpit) and my left ‘supraclavicular fossa’ (SCF) lymph nodes (clavicle). These were found on Octreoscan but at the time, they were not pathologically enlarged – just ‘lighting up’. They also light up on Ga68 PET.
In early 2012, 15 months after removal of primary and 10 months after liver resection, one of the axillary lymph nodes became palpable (signs of growth) and this coincided with a small spike in Chromogranin A. A total of 9 nodes were removed very shortly after this surveillance, 5 of which tested positive for NETs (Ki-67 <5%). As part of the same operation, 5 SCF left clavicle nodes were removed but tested negative. On a subsequent Octreoscan, the armpit was clear but the clavicle area still lit up. However, there is no pathological enlargement or pain – so this is just monitored. Also lights up on Ga68 PET I have a 3mm lung ‘nodule’, discovered in 2011. Apparently, lung nodules are a pretty common incidental finding with 1 per 500 X-rays and 1 per 100 CT scans finding them. This is monitored.
I have a 19mm thyroid ‘lesion’ which was pointed out to me in 2013. This has been biopsied with inconclusive results. Although the thyroid is an endocrine gland, it looks like a non-NET problem to date. Thyroid nodules are in fact very common and statistically, 50-70% of all 50-70 year olds will have at least one ‘nodule’ present (i.e. if you are in your 50s, there is a 50% chance you will have one nodule and so on). The vast majority will never bother a person while they live. That said, my thyroid blood tests are abnormal and on 20th March 2018, following an Endocrine appointment, I was put on a trial dose of 50mcg of Levothyroxine to counter the thyroid panel results indicating hypothyroidism. Levothyroxine is a thyroid hormone replacement. Early in 2017, during my Endocrine MDT, a surveillance ultrasound spotted a slightly enlarged lymph node on the right side (measuring 9mm x 9mm) described as a ‘level 4’ node (a location indicator meaning the ‘lower jugular group’). The report was passed to the NET MDT for their consideration with the surgical rep on the Endocrine MDT recommending a conservative approach – the NET MDT agreed. I suspect that’s right, it’s still below the worry threshold, nothing is palpable (no lumps) and I don’t have any specific symptoms. There could have been a number of reasons for the enlargement and it might even be back to normal size on my next scan (spoiler alert – it was). All my issues have been left-sided to date, so that was interesting. That said, I did have an MRI in 2014 to investigate pain and a swelling at the site of my right ‘sternoclavicular’ joint – subsequently declared a non-issue. Showed as inflammation on recent Ga68 PET.
Life as a metastatic Neuroendocrine Cancer patient is interesting and efficient surveillance is absolutely critical.
Scanning is a key diagnostic support and surveillance tool for any cancer. Even though you have elevated bloods or urine (….or not), a picture of your insides is really like a thousand words…. and each picture has a story behind it. Scanning can be a game changer in the hunt for tumours and although scans do not normally confirm the cancer type and grade, they certainly help with that piece of detective work and are key in the staging of the cancer.
When I read stories of people in a difficult diagnosis, I always find myself saying ‘a scan might resolve this’ and I always suggest people should try to get one. Even in the case of a story about late diagnosis or a misdiagnosis, I find myself thinking ‘if only they had done a scan earlier’. Despite what you read on NET forums, a CT scan will be able to find some evidence of tumour activity in 90-95% of cases. However, some are cunningly small or hiding and it can be like trying to find a needle in a haystack.
However, scans are not an exact science…..not yet! Apart from human error, sometimes tumours are too small to see and/or there are issues with ‘pickup’ (i.e. with NETs, nuclear scans need efficient somatostatin receptors). The differences between scan types are more quality (sensitivity) related as new technologies are introduced.
As for my own experience, I was very lucky. I managed to get a referral to a specialist early on in my diagnosis phase. He looked at the referral notes and said “what are you doing this afternoon“. I replied “whatever you want me to do“. He didn’t know I had cancer but his instincts led him to believe he needed to see inside my body, he wanted to scan me. The scan results were pretty clear – I had a metastatic Cancer and further checks were now needed to ascertain exactly what it was. So I took my seat on the roller coaster. Medicine is not an exact science (not yet anyway) but here’s something I believe is a very common occurrence in all cancers – If your doctors don’t suspect something, they won’t detect anything.
There’s frequent discussion about the best types of scans for different types of NETs and which is best for different parts of the anatomy. There’s also different views on the subject (including in the medical community), However, a few well known facts can be gleaned from authoritative NET sources:
Computed Topography (CT)
CT scans are often the initial imaging study for a patient presenting with signs or symptoms suggestive of many cancers including NET. These studies are most useful for disease staging and surgical planning as they provide excellent anatomic detail of the tumors themselves and surrounding structures. Primary NETs (GI and lung NETs) and their metastases are generally hyperenhancing with IV contrast and are best seen in the arterial phase of a triple phase CT scan.
In primary NETs, the average sensitivity of a CT scan is 73%. CT scans have even better sensitivity in detecting NET metastases, as they demonstrate 80% sensitivity for liver metastases (but see MRI below) and 75% sensitivity for other metastases (non-liver). This modality is also useful when the primary tumor site is unknown. In one single-institution retrospective study, it was the most common study ordered to look for an unknown primary tumor site and was able to uncover the primary in 95% of cases.
Magnetic resonance imaging (MRI)
MRI is the best conventional study to detail liver metastases in NETs. It is not as useful as CT for the detection of primary small bowel lesions or their associated lymphadenopathy, but is good for the detection of primary pancreatic NETs. A study comparing MRI, CT and standard somatostatin receptor-based imaging (OctreoScan) reported 95.2% sensitivity for MRI, 78.5% sensitivity for CT and 49.3% sensitivity for the OctreoScan in detecting hepatic metastases. MRI also detected significantly more liver lesions than the other two modalities.
You may see something called Magnetic Resonance Cholangiopancreatography (MRCP). Magnetic resonance cholangiopancreatography (MRCP) is a special type of magnetic resonance imaging (MRI) exam that produces detailed images of the hepatobiliary and pancreatic systems, including the liver, gallbladder, bile ducts, pancreas and pancreatic duct.
The primary role of conventional ultrasound in neuroendocrine disease is detection of liver metastases and estimation of total liver tumor burden. This technique has the advantages of near-universal availability, intraoperative utility, minimal expense and lack of radiation. Most examinations are performed without contrast, which limits their sensitivity (compared with CT and MRI). I know in my own situation, US was used as a quick check following identification of multiple liver metastasis during a CT scan. I’ve also had US used to monitor distant lymph nodes in the neck area but always in conjunction with the most recent CT scan output.
Endoscopic Ultrasound (EUS)
With increased access to endoscopy, NETs in the stomach, duodenum, and rectum are increasingly incidentally detected on upper endoscopy and colonoscopy. Patients are frequently asymptomatic without any symptoms referable to the a NET (i.e. non-functional). EUS has also been used to survey patients at increased risk of developing pancreatic NETs. For example, patients with multiple endocrine neoplasia (MEN). They are also frequently used in conjunction with biopsies using fine needle aspiration (FNA) guided by EUS.
18-Fluoro-Deoxy-Glucose PET (FDG PET) is used to detect malignancy for a variety of tumor types. Unfortunately, its utility has not been borne out in NETs, as the majority of NETs tend to be relatively metabolically inactive and fail to take up the tracer well. However, high-grade NETs are more likely to demonstrate avid uptake of 18FDG, giving these scans utility in identifying tumors likely to display more aggressive behavior.
The use of Fluoro-18-L-Dihydroxyphenylalanine (18F-FDOPA) in PET was developed in the 80’s for the visualisation of the dopaminergic system in patients with degenerative disorders, such as Parkinson’s Disease and related disorders. The ﬁrst publication on the use of 18F-FDOPA PET for brain imaging was in 1983, which was followed by many others on the use of 18F-FDOPA PET for the diagnosis of Parkinson’s disease. Years later, in 1999 the ﬁrst publication on the use of 18F-FDOPA PET for imaging of neuroendocrine tumour appeared. The value of 18F-FDOPA PET has now been proven for the diagnosis and staging of many neuroendocrine tumours, brain tumours and congenital hyperinsulinaemia of infants.
18F-FDOPA is accurate for studying well differentiated tumours. However the difficult and expensive synthesis have limited its clinical employment. It currently can be successfully used for imaging tumours with variable to low expression of somatostatin receptors (SSTR) such as Medullary Thyroid Carcinoma, Neuroblastoma, Pheochromocytoma), and others that cannot be accurately studied with Somatostatin SSTR scans such as the OctreoScan (Somatostatin Receptor Scintigraphy (SRS)), which uses the ligand 111In-DPTA-D-Phe-1-octreotide or the newer 68Ga DOTA-peptides.
Radioiodinated (123I) metaiodobenzylguanidine (MIBG) is an analog of norepinephrine that is used to image catecholamine-secreting NETs such as pheochromocytomas, paragangliomas and glomus tumors. It can also be used to look for Neuroblastoma in children. In patients with functional pheochromocytomas or paragangliomas, this modality has a sensitivity of 90% and positive predictive value of 100%. However, it has limited use in Gastrointestinal (GI) NETs, as this modality was positive in only 49.1% of patients. In the same cohort of patients, OctreoScan was positive in 91.2%. As an imaging tool, this study is best used to confirm a diagnosis of pheochromocytoma or paraganglioma and define the extent of metastatic disease in these tumors. (Note – the Ga68 PET is rising in prominence though). Its most practical use in GI NETs may be to determine whether patients with metastases may benefit from treatment with 131I-MIBG (a form of radiotherapy).
Somatostatin receptor-based imaging techniques
Somatostatin is an endogenous peptide that is secreted by neuroendocrine cells, activated immune cells and inflammatory cells. It affects its antiproliferative and antisecretory functions by binding to one of five types of somatostatin receptors (SSTR1- SSTR5). These are G-protein coupled receptors and are normally distributed in the brain, pituitary, pancreas, thyroid, spleen, kidney, gastrointestinal tract, vasculature, peripheral nervous system and on immune cells. Expression of SSTRs is highest on well-differentiated NETs. Somatostatin receptor type 2 is the most highly expressed subtype, followed by SSTRs 1 and 5, SSTR3 and SSTR4.
It must be noted that even the most modern scans are not an exact science. Radionuclide scans are like conventional imaging, they can be subject to physiological uptake or false positives, i.e. they can indicate suspicious looking ‘glows’ which mimic tumours. This article explains it better than I can – click here.
The ubiquity of SSTRs on NET cell surfaces makes them ideal targets for treatment (e.g. Somatostatin Analogues (Octreotide/Lanreotide) and PRRT), but also for imaging. There are two primary types of somatostatin receptor-based imaging available:
Octreoscan – In111 based
The most common (currently) is the OctreoScan or Somatostatin Receptor Scintigraphy (SRS), which uses the ligand 111In-DPTA-D-Phe-1-octreotide and binds primarily to SSTR2 and SSTR5. In its original form, it provided a planar, full body image. In modern practice, this image is fused with single photon emission computed tomography (SPECT) and CT. This takes advantage of the specificity of the OctreoScan and the anatomic detail provided by SPECT/CT, improving OctreoScan’s diagnostic accuracy. These improvements have been shown to alter the management in approximately 15% of cases, compared with just OctreoScan images. In primary tumors, the OctreoScan’s sensitivity ranges from 35 to 80%, with its performance for unknown primary tumors dipping beneath the lower end of that range (24%). Its ability to detect the primary is limited by the size but not SSTR2 expression, as tumors less than 2 cm are significantly more likely not to localize but do not have significantly different SSTR2 expression than their larger counterparts.
Octreoscan – Tc99m based
In one study, it was shown that sensitivity and negative predictive
values of Tc-99m-Octreotide scan is significantly higher than that of CT
and MRI. Using Tc-99m instead of In-111 had several advantages that
include better availability, cheaper and higher quality images. In
addition, to less radiation exposure to both patients and nuclear
medicine personnel. In the absence of Ga68 PET, this could prove a reliable alternative. Please note this scan is completed in a single day vs In111 Octreotide time of 2-3 days.
Ga68 PET (or SSTR PET in general)
The newest somatostatin receptor-based imaging modality, although it has been around for some time, particularly in Europe. The most common of these labeled analogs are 68Ga-DOTATOC, 68Ga-DOTANOC and 68Ga-DOTATATE. They may be known collectively as ‘SSTR-PET’. Additionally, the DOTATATE version may often be referred to as NETSPOT in USA but technically that is just the commercial name for the radionuclide mix.
These peptides are easier and cheaper to synthesize than standard octreotide-analog based ligands, boast single time point image acquisition compared to 2 or 3 days with Octreoscan. Its superior spatial resolution derives from the fact that it measures the radiation from two photons coincidentally. SPECT, in comparison, measures the gamma radiation emitted from one photon directly. This results in different limitations of detection – millimeters for 68Ga-PET compared with 1 cm or more for SPECT. There are a few choices of ligands with this type of imaging, but the differences lie primarily in their SSTR affinities – all of the ligands bind with great affinity to SSTR2 and SSTR5. 68Ga-DOTANOC also binds to SSTR3. Despite these differences, no single 68Ga ligand has stood out as the clear choice for use in NETs. As with standard somatostatin receptor-based imaging, these 68Ga-PET studies are fused with CT to improve anatomic localization.
Comparison studies between 68Ga-PET and standard imaging techniques (CT, OctreoScan) have universally demonstrated the superiority of 68Ga-PET in detection of NET primary tumors and metastases. Two early studies compared 68Ga-DOTATOC to standard somatostatin imaging (SRS)-SPECT and CT. Buchmann et al. reported that 68Ga-DOTATOC detected more than 279 NET lesions in 27 patients with histologically proven NETs, whereas SRS-SPECT detected only 157. The greatest number of lesions were detected in the liver. 68Ga-DOTATOC found more than 152 hepatic lesions, while SRS-SPECT found only 105, resulting in a 66% concordance rate between the two modalities. The concordance for abdominal lymph nodes was worse at 40.1%. Cleary these advantages are going to impact on treatment plans, some needing to be altered. In addition, 68Ga-DOTA PET imaging can be used to determine which patients might benefit from use of Somatostatin Analogues (Octreotide/Lanreotide) and PRRT – you can read more about this integrated and potentially personalised treatment in my article on ‘Theranostics‘ – click here.
It’s worth pointing out that SSTR PET is replacing previous types of radionuclide scans, mainly Octreoscan (Indium 111) and is not replacing conventional imaging (CI) such as CT and MRI etc. Whilst SSTR-PET has demonstrated better sensitivity and specificity than CI and In-111, there are specific instances in which SSTR-PET is clearly preferred: at initial diagnosis, when selecting patients for PRRT, and for localization of unknown primaries. For patients in which the tumor is readily seen on CI, SSTR-PET is not needed for routine monitoring. The Journal of Nuclear Medicine has just published “Appropriate Use Criteria for Somatostatin Receptor PETImaging in Neuroendocrine Tumors” which gives guidance on it’s use – issued by the Society of Nuclear Medicine and Molecular Imaging (SNMMI).
Parathyroid Scan – Sestamibi
Sestamibi scanning is the preferred way in which to localize diseased parathyroid glands prior to an operation. This parathyroid scan was invented in the early 1990’s and now is widely available. Sestamibi is a small protein which is labeled with the radio-pharmaceutical technetium99 (Tc99m). This very mild and safe radioactive agent is injected into the veins of a patient with hyperparathyroidism (parathyroid disease) and is absorbed by the overactive parathyroid gland. Since normal parathyroid glands are inactive when there is high calcium in the bloodstream, they do not take up the radioactive particles. When a gamma camera is placed over the patient’s neck an accurate picture will show the overactive gland. Only the overactive parathyroid gland shows up…a very accurate test.
The Sestamibi scan will display the hyperactive gland which is causing hyperparathyroidism in about 90 percent (90% sensitivity) of all patients. If the Sestamibi does show the hyperactive gland it is almost always correct (98-100% specificity). It takes approximately two hours to perform the Sestamibi scan after it has been injected. Pictures of the neck and chest are usually taken immediately after the injection and again in 1.75 to 2.0 hours (shown above). Newer techniques allow for more complete two and three dimensional images to be obtained of a patient’s neck. This technique is called SPECT scanning (Single Proton Emission Computerized Tomography) but it is usually not necessary.
Taking the camera inside and directly to the Tumour
Of course there are other ways to “see it” via several types of Endoscopy procedures – taking the camera to the tumour. Read my article about this by clicking here
A look to the future of PET Scans
Just imagine something which is 40 times better than current PET scan technology? That’s what the scientists are working on now. Here’s an example called “EXPLORER“. Clearly there are more answers required in order to see if this is suitable for use with NETs (i.e. will it work with our radionuclide tracers etc) but it is very exciting and like something out of Star Trek. A little bit of me is worried about ‘overdiagnosis’ so interpretation of something that detailed will be very important to avoid unnecessary worry. Read more here and there is a later update here. Check out this cool video of the 3D images:
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Scanning is a key diagnostic and surveillance tool for any cancer. Even though you have elevated bloods or urine (….or not), a picture of your insides is really like a thousand words…. and each picture has a story behind it. Scanning can be a game changer in the hunt for tumours and although scans can’t (yet) confirm the cancer type and grade, they certainly help with that piece of detective work and are key in the staging of the cancer.
When I read stories of people in a difficult diagnosis, I always find myself saying ‘a scan might resolve this’ and I always suggest people should try to get one. Even in the case of a story about late diagnosis or a misdiagnosis, I find myself thinking ‘if only they had done a scan earlier’. Despite what you read on NET forums, a CT scan will normally find some evidence of most tumour activity.
However, scans are not an exact science…..not yet! Apart from human error, sometimes tumours are too small to see and/or there are issues with ‘pickup’ (i.e. with NETs, nuclear scans need efficient somatostatin receptors). However, technology is improving all the time and you can read about this in my blog Neuroendocrine Cancer – Exciting times Ahead.
As for my own experience, I was very lucky. I managed to get a referral to a specialist early on in my diagnosis phase. He looked at the referral notes and said “what are you doing this afternoon”. I replied “whatever you want me to do”. He wanted to scan me. He didn’t know I had cancer but his instincts led him to believe he needed to see inside my body. The scan results were pretty clear – I had a metastatic Cancer and further checks were now needed to ascertain exactly what it was. So I took my seat on the rollercoaster. Here’s something I always say I believe is so much better than the impractical early diagnosis messages that seem to pervade our community: If your doctors don’t suspect something, they won’t detect anything and I believe this is a very frequent outcome of many diagnoses for many cancers (not just NETs).
There’s frequent discussion about the best types of scans for different types of NETs and even for different parts of the anatomy. This is correct and there’s also different views on the subject (including in the medical community), However, a few well known facts that can be gleaned from authortative NET sources. I found this useful video summary from the NET Patient Foundation describing the different scans for NET Cancer and what to expect. Worth a look.
Sooner we can all get access to the latest radionuclide scans the better!