Although initially considered rare tumours, the most recent data indicates the incidence of NETs has increased exponentially over the last 4 decades and they are as common as Myeloma, Testicular Cancer, and Hodgkin’s Lymphoma. In terms of prevalence, NETs represent the second commonest gastrointestinal malignancy after colorectal cancer.
In fact, the graph of the SEER database from 2004 indicated that the rate of incidence increase was faster than any other cancer on the planet, this particular rise in incidence was mainly attributed to lung, small intestine, and rectal NETs (but see latest SEER database output on you read on). However, since the World Health Organisation’s revised classification of Neuroendocrine Neoplasms in 2010, there would be a significant increase if this data exercise was run again. This is due to the abandonment of the division between benign and malignant NETs following the 2010 declaration that all NETs now have malignant potential and are graded accordingly. The 2004 SEER data compiled did not take into account benign NETs.
However, the most recent USA study up to 2012 has confirmed the incidence beyond 2004 has continued to rise (and rise, and rise, and rise) and this is covered below in the section entitled “Meanwhile in USA”.
Incidence and Prevalence
Before I continue, it’s important to understand the difference between incidence and prevalence. In the crudest of terms, incidence is the number of new cases of a disease being diagnosed (normally aligned to a specific quota of the population per year, generally 100,000). Prevalence normally indicates an amount of people living at any one time with a disease. It’s also important to note that different nations or groups of nations classify ‘rare’ in different ways – not really helpful when looking at worldwide statistics.
So why the increase? I suspect the reasons include (but are not limited to), more awareness (population and medical staff), better detection techniques and probably more accurate reporting systems, at least in USA, Norway, Canada and now in the UK i.e. a mixture of underdiagnoses and misreporting. The Canadian study is important as it also noted the proportion of metastases at presentation decreased from 29% to 13%. This is the first study that suggests an increased incidence of NETs may be due to an increased (and earlier?) detection. This has the knock on effect of increasing prevalence as most NET Cancer patients will normally live for longer periods. Add to this the plethora of better treatments available today, you have a highly prevalent cancer. Mostg of that is good news.
However, their true incidence may be higher owing to the lack of diagnosis until after death. For example, in USA, a respected NET specialist stated that the autopsy find for (excuse the outdate terminology) ‘carcinoid‘ is 4 times the recorded diagnosis rate. In Australia, one study claimed that 0.05% of all autopsies found a Pheochromocytoma or Paraganglioma. A very interesting slideshow from a well respected NET expert claimed there are 200,000 undiagnosed NET patients in USA. Slide below: You may also wish to check out my article “The Invisible NET Patient Population” where this is explored further.
US SEER 2004 – The Trigger and Turning Point
In the largest study of its kind up to that point, well-known Neuroendocrine Cancer expert James C. Yao researched the Surveillance, Epidemiology and End Results (SEER) database. His team studied 35,825 cases of Neuroendocrine Cancers in the United States covering data between 1973 and 2004. The report concluded that in 2004 there were 5.25 new cases of NETs per 100,000 people, compared with 1.09 per 100,000 in 1973 . This is in contrast to the overall incidence of malignancies, which has remained relatively constant since 1992 (see the yellow line on the graph). The study also pointed out that due to increased survival durations over time, NETs are more prevalent than previously reported. If you analyse the NET data for 1994 (10 years before the end of the study period), you will see an incidence rate of approx 3.25/100,000. In 2004, the incidence rate had risen to 5.25/100,000. Although not an exact science, it does suggest the potential incidence rate at 2014 (10 years after the study period) might possibly have climbed well beyond 6/100,000 and even further if the same rate of increase displayed by the study had continued. This study also confirmed a prevalence of 103,000 NET patients as at 2004. As this is regarded as the most accurate NET statistic ever produced, it is interesting to note that was at a time when the prognostics for NET were not as good as they are today indicating there must be a very significant increase by 2017. Moreover, this was prior to the WHO 2010 reclassification of NETs so more diagnoses will be counted today that were not counted in 2004. See below to see the significance of this figure (see section ‘Do the math’).
This is an astonishing set of statistics – particularly as they are based on data which was 12 years old. However, there is now new data up to 2012 that overtakes the above-mentioned groundbreaking study and confirmed the incidence is now even higher. See section entitled “Meanwhile in USA …….”
Meanwhile in Norway ……
Data from the Norwegian Registry of Cancer showed a similar incidence of Neuroendocrine Cancers with a 72% increase between 2000 and 2004 compared with 1993–1997 . Also in Norway, an article published in 2015 entitled “Epidemiology and classification of gastroenteropancreatic neuroendocrine neoplasms using current coding criteria” indicated a high crude incidence of GEP-NEN, at 5·83 per 100 000 inhabitants over the period 2003-2013 (adjusting to 7.64 for Europe in 2013 – see diagram below extracted from cited article 2a). It was also noted together with the statement “….a significant increasing trend over time”. [2a] Citation [2b]
Meanwhile in Canada …….
CNETs have highlighted an article published in the magazine ‘Cancer’, February 15, 2015, showing that the incidence of Neuroendocrine Tumours has markedly increased in Canada over the course of 15 years (1994-2009). The results showed that the incidence of Neuroendocrine Tumours has increased from 2.48 to 5.86 per 100,000 per year.  
Meanwhile in UK …….
The latest figures from Public Health England (PHE) indicate the incidence of NETs has risen to 8/100,000 (i.e. not rare) using the latest International Classification of Diseases for Oncology (ICD-O) methodology version 3 – ICD-O-3. That means a new NET diagnosis every 2 hours. You can see a summary of the report here which is based on 8,726 cases: NEW: Public Health England release new incidence data for Neuroendocrine Cancer
Meanwhile in New Zealand …….
Meanwhile in USA …….
The latest evidence of its rise is contained in the largest ever study ever conducted. It is based on data up to 2012 so it’s worth noting that this data is now 5 years old (3 years for the project prevalence figure), so even these figures may still be conservative. The document, which was published in 2017 can be found here: Click here. A short summary follows:
In this population-based study that included 64 971 patients with neuroendocrine tumors, age-adjusted incidence rates increased 6.4-fold between 1973 and 2012, mostly for early-stage tumors. Survival for all neuroendocrine tumors has improved, especially for distant-stage gastrointestinal and pancreatic neuroendocrine tumors.
Of the 64 971 cases of NETs, 34 233 (52.7%) were women. The age-adjusted incidence rate increased 6.4-fold from 1973 (1.09 per 100 000) to 2012 (6.98 per 100 000). This increase occurred across all sites, stages, and grades. In the SEER 18 registry grouping (2000-2012), the highest incidence rates were 1.49 per 100 000 in the lung, 3.56 per 100 000 in gastroenteropancreatic sites, and 0.84 per 100 000 in NETs with an unknown primary site. The estimated 20-year limited-duration prevalence of NETs in the United States on January 1, 2014, was 171 321
Conclusion: The incidence and prevalence of NETs have continued to rise in the United States, owing to the increased diagnosis of early-stage disease and possibly stage migration. The survival of patients with NETs has improved, and this improvement has been greater for those with distant gastrointestinal NETs and, in particular, distant pancreatic NETs.
Combine that with a revised annual incidence rate of 23,000 and the very well known fact that NETs is a highly prevalent disease, it must be mathematically impossible for the figure not to be above the USA rare threshold of 200,000 in 2017. As you can see from the graph below, the incidence rate for NETs continues to outstrip the incidence rate for all malignant neoplasms (another word for tumour). Amazingly, the report authors even state “…….. it is likely that we have underestimated their true incidence and prevalence”.
The NET Research Foundation published an amazing infographic which summarises the output of the SEER 2012 study. See it below and you can read the accompanying text here.
Do the Math
So it seems that Neuroendocrine Cancer is not only the fastest growing cancer in incidence terms but as a group of cancers, it is no longer rare in statistical terms. For example, if you roughly extrapolate the US SEER data graph above to 2017 and recalculate the prevalence rate based on 23 000 per year from the 2014 figure of 171 321. Unfortunately, some people will have passed, but it’s well documented as a highly prevalent cancer and therefore more people live. The prevalence of neuroendocrine tumors in USA was higher than the combined estimated prevalence of esophageal cancer (n = 36,857), gastric adenocarcinoma (n = 79,843) and pancreatic adenocarcinoma (n = 49,620) in 2013. In fact, one of the conclusions of the 2012 SEER report is that we are living longer with NETs. This is in line with many other cancers due to improved diagnostic and treatment regimes. Cleary more work still needs doing.
Whilst reporting has been improved, it is most likely still not 100% accurate. Therefore, even the figures above may be understated due to an incorrect cause of death reporting and incorrect diagnosis/recording of the wrong cancers (e.g. pNETs recorded as Pancreatic Cancer, Lung NETs recorded as Lung Cancer, etc). This is certainly still happening in UK and I suspect in most other countries. Add to that the regular reports of Neuroendocrine Tumours being found during autopsies and you have the potential for an even further unrecorded increase had these been found prior to death. In fact, according to SEER 2012, the true incidence and prevalence is most likely underestimated. You may also wish to check out my article “The Invisible NET Patient Population” where this is explored further.
The issue is also complicated by the method used in USA for naming a disease ‘rare’. Rather than use incidence rates, the USA uses the number of people living with the disease at any one time (i.e. essentially the prevalence). This is currently 200,000 as a threshold – anything below that is considered rare. It seems mathematically impossible for NETs to be less than 200,000 given the data provided above.
When I first started researching NETs back in 2010, the US figure (which varies from source to source) was around 125-150,000. Why are people quoting figures less than this in 2017 when the 2014 figure has now been confirmed above? There also seems to be a selective omission of hte new US incidence rate of 7/100,000.
You will also see that Dana Farber is estimating more than 200,000 people are as yet undiagnosed. Even if that were 50% accurate, it would put the current prevalence figure in US over 300,000.
Let’s cut to the chase – NETs are not rare, they are just less common
Are we shouting loud enough about this? I don’t think so. ‘Rare’ is very frequently used within our community almost to the point of being a status symbol (not sure why – to be rare is to be ignored). Based on these figures, this looks like an outdated approach along with its associated icons. Statistically, rare cancers don’t normally do well in comparison to the more common types and they certainly don’t attract the same resources and research.
“A neoplasm on the rise. More prevalent than you may think. Incidence increased dramatically during past 3 decades” (Novartis)
“it’s less rare than we used to think. It’s more malignant than we previously thought” (Dr Richard Warner)
“…..it is one of the most rapidly increasing cancers in the U.S. There has been a 500-percent increase in the last 30 years” (Dr Edward Wolin)
“Estimated more than 200,000 undiagnosed cases in the US” (Dana Farber)
“Neuroendocrine Cancer – it’s not rare, it’s less common. We need a new paradigm” (Ronny Allan)
Thanks for reading