
Neuroendocrine Tumours (NETs) – Vitamin D (Cholecalciferol / Ergocalciferol)
Vitamin D deficiency is demonstrably more common in people with neuroendocrine tumours (NETs) — but that does not automatically mean your deficiency is caused by

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It’s no secret that Neuroendocrine Neoplasms (NENs) can be difficult to diagnose, particularly well differentiated slow growing types (NETs) which can sometimes be difficult to see. Plus, many patients present with relatively routine day to day symptoms suggesting a myriad of day-to-day illnesses seen daily in every GP/PCP practice.
But conversely, many are found incidentally while checking for something else, or in reaction to a visit to the ER/A&E or as a referral by primary care physicians for further checks at secondary facilities. A few examples:
1. Most appendiceal NETs are found when patients present with pain in the right lower quadrant i.e. symptoms of appendicitis. The resulting appendectomy will find the tumour. However, it’s true to say that most appendectomies will be connected to appendicitis with no NET involvement. Nonetheless, the number of NETs discovered this way is significant, but most will be removed with curative intent. They rarely metastasise at the lower grades.
2. Many Gastric NETs are found when investigating symptoms of heartburn/acid reflux issues. They are almost always found by simple endoscopy checks using cameras and needle biopsies. They rarely metastasise at the lower grades.
3. Many Rectal NETs are being found via colonoscopies when investigating symptoms of abdominal issues plus (e.g.) as a follow up to abnormal tests on faecal immunochemical test (FIT) as part of regular government cancer screening initiatives. Like appendiceal NETs, most of these will be removed with curative intent. They rarely metastasise at the lower grades.
4. More and more small intestine NETs are being found via extended colonoscopies (based on the common location of the terminal ileum) plus as a follow up to abnormal tests on faecal immunochemical test (FIT) as part of regular government cancer screening initiatives.
5. More and more pancreatic NETs are being found a combination of endoscopy examinations and conventional imaging.
6. Diagnoses of Lung NETs can be triggered by simple x-rays checking for things such as chest infections.
7. Often, doctors move straight to imaging where abnormalities can be spotted which warrants further and deeper investigation.
Most of the above can also be applied to Neuroendocrine Carcinomas (NECs), a poorly differentiated type of NEN.
Despite what you see in patient groups and statistics pushed out by certain organisations, most NETs are localised (i.e. low stage) and grade 1. These statistics can be seen in the SEER US NET study published in 2017 (based on data up to 2012) – this document can be found in my “Not as rare as you think” blog post here. When you consider the game changers below, this should hopefully confirm/improve this situation when new statistics come out in this new era of better imaging and earlier diagnoses. An update to the above SEER dataset is due sometime in 2025 (in fact it’s well overdue).
As we progress, so does science. Consequently, imaging is playing a part in finding many cancers earlier and quicker, including NETs. In addition to the regular approaches above and the incidental findings which do help in early-stage diagnosis, those who are referred for conventional imaging have another chance of an early-stage diagnosis. It’s not true to say that undiagnosed NETs are never found on conventional imaging (scopes/xray/CT/MRI. I’m fairly confident that if statistics existed, most NET diagnoses are based on findings of conventional imaging and scopes. But add nuclear imaging which is advancing at a phenomenal rate compared to 10 years ago, the chances of finding NETs have been exponentially increased. The difficulty is getting to the stage of carrying out nuclear imaging, there can be several hurdles to jump not least the availability of PETs and nuclear radioligands.
I am seeing more and more early-stage NETs in my patient group in difficult to diagnose primary sites where many are diagnosed at a late stage meaning an incurable cancer with long term surveillance and reduced prognosis. e.g. Small Intestine NETs and Pancreatic NETs.

Most of the above can also be applied to Neuroendocrine Carcinomas (NECs), a poorly differentiated type of NEN, although different types of nuclear imaging might be needed.
Imaging cannot take all the credit though. More and more doctors (but still not enough) are becoming aware of NENs via foundation organisations such as NET Research Foundation, Neuroendocrine Cancer UK, Neuroendocrine Cancer Australia and the PheoPara Alliance (Pheochromocytoma/Paraganglioma). There are many more, but some remain fixated in other areas, hopefully they will catch up soon.
The awareness issue is also obfuscated by continued and unnecessary use of the term “carcinoid” including within the healthcare community. If they would just update themselves with the latest World Health Organisation (WHO) classification systems, they would realise how out of date they are. Ditto to any patient foundation organisation or patient group.
The other key fact coming out in 2023 is the continuation of a theme which has been improving since 2015, the fact that NENs are no longer rare. One major US cancer organisations underscored this awareness improvement earlier this year by very clearly stating that “NETs are uncommon but definitely not rare“. They also astonishingly went on to say the false perception that NET is a rare cancer has held back proper clinical research.
Worth pointing out that in UK and Australia, diligent and accurate cancer registry analysis put NENs as the 10th and 7th most prevalent cancers in those countries.
My own thinking is that if primary and secondary care doctors were all made aware of this fact, NETs might be something doctors would consider more rather than dismiss it as being a very unlikely diagnosis.
I am not a doctor or any form of medical professional, practitioner or counsellor. None of the information on my website, or linked to my website(s), or conveyed by me on any social media or presentation, should be interpreted as medical advice given or advised by me.
Neither should any post or comment made by a follower or member of my private group be assumed to be medical advice, even if that person is a healthcare professional. Some content may be generated by AI which can sometimes be misinterpreted. Please check any references attached.
Please also note that mention of a clinical service, trial/study or therapy does not constitute an endorsement of that service, trial/study or therapy by Ronny Allan, the information is provided for education and awareness purposes and/or related to Ronny Allan’s own patient experience. This element of the disclaimer includes any complementary medicine, non-prescription over the counter drugs and supplements such as vitamins and minerals.
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