By Anna C. Greene, PhD, NETRF Chief Scientific Officer
In recent years, you may have seen headlines and commentaries suggesting that neuroendocrine cancers are “no longer rare.” These claims often point to rising diagnosis rates and the growing number of people living with neuroendocrine cancer.
Those trends are important and should lead to greater attention, resources, and urgency for this community. But a bigger umbrella number does not automatically make answers easier to find or cures faster to achieve.
When a cancer is rare, patients often feel it immediately: fewer experts, fewer studies, fewer clinical trials that fit, and more decisions made with incomplete evidence. For researchers, rarity changes the playbook; multicenter collaboration, shared registries, and smarter trial designs become necessities, not “nice to have.”
In this post, we clarify how “rare” is defined in cancer, and why grouping neuroendocrine cancers together can change the headline without changing the research bottleneck.
Two ways “rare” is discussed
“Rare” can mean incidence (new cases each year) or prevalence (people living with the disease, often discussed in orphan drug policy), and conflating the two causes confusion.
Rare cancer: incidence thresholds
- In the United States, the National Cancer Institute defines a rare cancer as occurring in fewer than 15 people per 100,000 per year.
- In Europe, ESMO defines rare cancers as fewer than 6 per 100,000 per year.
This is the “rare” definition that matters most for research feasibility: small numbers make it hard to recruit trials, compare treatments, and build strong evidence.
Orphan drug designation: prevalence thresholds
In the US, the Food and Drug Administration (FDA) grants orphan drug designation to therapies intended to treat diseases or conditions that affect fewer than 200,000 people. Orphan drug designation is intended to encourage the development of treatments for smaller patient populations. It is typically applied to a specific drug for a specific indication, rather than as a permanent label for an entire cancer family.
The two yardsticks behind “rare”
Incidence = how many people are newly diagnosed each year.
Prevalence = how many people are living with the diagnosis right now.
That means a cancer can be:
- Rare by incidence but not orphan by prevalence: few new diagnoses each year, but many people living with it because survival can be long.
- Orphan by prevalence but not rare by incidence: many new diagnoses each year, but fewer people living with it at any moment because survival may be short.
- Both rare and orphan.
- Neither, depending on how the disease is defined and grouped.
This is why “rare” debates can get stuck; they are often comparing different yardsticks.
So, are neuroendocrine cancers rare?
It depends on how you define “rare,” but many neuroendocrine cancers are still rare where it matters most, at the level of the specific diagnosis. Neuroendocrine cancers are an umbrella term covering many distinct diseases across primary sites, grades, and biology, including both neuroendocrine tumors and neuroendocrine carcinomas. Grouped together, the overall numbers can look larger. However, patients are treated for specific diagnoses, and many of those remain rare in ways that affect research feasibility.
That is why “not rare anymore” can be both true and misleading. Rising recognition and diagnosis should drive more attention and investment, but changing the headline does not remove the small-numbers bottleneck that slows trials and limits evidence. This is where the gap between visibility and solvability becomes clear.
What visibility does not solve
Even when the umbrella category looks larger, it does not automatically create:
- enough patients at one site to run a trial
- enough tissue samples to validate biomarkers quickly
- enough comparable data to know which treatments truly work best
To move faster, we have to solve the small-numbers problem directly.
What speeds progress
Progress comes from infrastructure built for rare diseases:
- multicenter trials designed for smaller populations
- shared registries and datasets so every patient’s experience adds to the evidence base
- shared biospecimens and standardized pathology so findings can be tested and reproduced
- efficient trial designs when classic large randomized trials are not feasible
This is why rare-cancer strategies remain essential for neuroendocrine cancers, even as the community’s visibility grows.
NETRF’s bottom line
We welcome the growing recognition that neuroendocrine cancers deserve far more attention than they have historically received. But we will not confuse visibility with solvability.
Calling the umbrella bigger may help the world notice, but curing faster requires building the infrastructure that makes small numbers scientifically powerful.
That is the rare-cancer challenge and the rare-cancer opportunity for the entire neuroendocrine community.
NETRF will continue to invest in collaborative science that turns small numbers into stronger evidence, faster. We invite the entire community to join us in that effort, whether by engaging with research, amplifying patient voices, or supporting the work that makes this possible.
____________________________________________________________________________________________
Read More
Neuroendocrine Cancer on the Rise: What the Latest Research Shows