In my post entitled “If you can see it, you can detect it“, I listed the different types of scanning techniques and technology to find evidence of disease in Neuroendocrine Tumours (NETs). Of course, while scans, blood and (current) marker tests can give some pretty big and important clues, “tissue is the issue” to determine type.
Even after formal diagnosis, seeing all the tumours can be a challenge with NETs. In the article I quoted above, I indicated that scans for NETs can be analogous to picking ‘horses for courses‘. For example, most NETs have somatostatin receptors and can often be seen better on functional scans e.g. somatostatin receptor scintigraphy (SRS) or somatostatin receptor PET (SSTR-PET), combined with the use of radionuclides designed specifically for this purpose e.g. In111, Tc99m, Ga68, Cu64. So, while you might see them on one scan, you may not see them on the other and vice versa (….. there are variables at play here). Now you see them, now you don’t!
There are other functional scans for various NET types, such as FDG PET which tends to be used for higher grade NETs and Neuroendocrine Carcinomas and those at the boundary of Grades 2 and 3 may also benefit. You can read about these scan types plus more by clicking here.
Even when they can be seen on conventional imaging e.g. CT, MRI, there are still some factors involved in getting the optimum view. For example, NETs are known for their hypervascularity, so viewing them on CT in the “late arterial phase” of a triple phase CT scan should present the best view. This is a really complex area and may not apply to every scenario. It’s my experience that some radiologists and personnel who order the scans are not aware of this requirement for NETs. This issue is graphically displayed below (click the picture for the source). Now you see them, now you don’t!
The MRI is said to be more sensitive for liver lesions, although the CT should be sufficient for many. The CT is said to be better than MRI for certain primary tumours including Small Intestine NETs (SI NET). I also noted some studies claiming the MRI may be better to pick up small liver tumours than a nuclear scan. So, for some people, a CT and/or an MRI may be an option for routine surveillance.
This link will explain some of the difficulties in identifying liver metastases using conventional imaging, this includes the use of particular types of contrast material (e.g. Evoist) on MRI – click here
The other CT issue which some of you may have encountered is a “fatty liver“. Diffuse hepatic steatosis is the technical name for fatty liver. It appears to be a common imaging finding (~25% of the population) and can lead to difficulties assessing the liver appearances, especially when associated with the less common focal fatty sparing. This is a complex area, and you should consult your specialist about how this might affect your imaging. Now you don’t see it (properly).
My own experience
When I was first diagnosed, my CT scans looked pretty clear. In fact, when you look at the lead picture in my post “If you can see it, you can detect it“, that’s a picture of my liver from a diagnostic CT scan, showing a big tumour staring you right in the face. So, CT was very successful in leading to my diagnosis. A follow-on Octreotide scan confirmed the staging, adding two more hotspots above the diaphragm (unusual for a SI NET). Following primary surgery, liver surgery and lymph node surgery, CTs and SRS/SSTR PET have done the job.
After my liver surgery in 2011, my surgeon said there were 6 sub-centimetre deposits left behind. My liver disposition was much more conspicuous on intraoperative ultrasound than my diagnostic CTs, and with significant right sided disease. I did try to track these remnant lesions over the years, I found it much easier in the first four year after diagnosis. Reading my surveillance CT scans in the last few years, I started to think they were disappearing, a nice thought.
My last three CT scans have been really interesting with the latest one on 6th November stating there was “no evidence of hepatic metastatic disease“. But before you jump for joy on my behalf, read on. Prior to that, April 2019 results said “barely visible as hypervascular blushes during arterial phase on the CT and this has not changed since April 2018. The November 2019 CT said, “diffuse fatty infiltration with no obvious focal lesions”. The same radiologist consultant carried out all my scans for the first 5 years after diagnosis and has mentioned the appearance of a fatty liver before, suggesting MRI would show the liver better (I had an MRI once to check on a chest lump but that was negative. I’m not too keen on MRIs due to some metal inside me!). The 2018 CT said, “no focal liver lesions”. Way back to 2017 and there is mention of “subtle hyperenhancement in the right lobe of the liver 11mm (seen only on arterial phase)”. I could go on …… Now you see them, now you don’t!
I’m not getting too excited about these CT results because my Ga68 PET/CT in June 2018 stated, “there are multiple foci of tracer uptake within both lobes of the liver, predominately in the right“. So, they were still loitering mid 2018 but overall, they don’t seem to be doing much (thankfully). The Ga68 PET scan results prompted my original surgeon to point out they were definitely more conspicuous on nuclear scan than on CT.
So, in the first half of next year, I will get a repeat Ga68 PET/CT with a consultation already pencilled in for July 2021. You can read about my experience of that by clicking here.
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