Rectal carcinoids are on the rise: early detection by screening endoscopy

Background

Colorectal cancer (colorectal adenocarcinoma) is largely preventable with regular screening and is treatable if detected early. Thanks to screening, the death rate from colorectal cancer is steadily declining in (Western) countries with established screening facilities.

Although adenocarcinoma is the most prevalent colorectal neoplasm, it is not the only one. The age-adjusted incidence of well-differentiated neuroendocrine tumors and cancers of the colorectum (colorectal carcinoids) is about 1 in 100 000 [1]. The Surveillance, Epidemiology, and End Results (SEER) registry database of the National Cancer Institute (which reflects the standard of care for the average US citizen) shows that the age-adjusted incidence of rectal carcinoids has increased about tenfold over the last 35 years [1] [2]. In the United States, 50 % or more of rectal carcinoids are nowadays diagnosed as “incidentally” identified lesions, due to the increased availability and use of screening sigmoidoscopy and/or colonoscopy [2]. The prevalence of rectal carcinoids in adults undergoing screening endoscopy (mean/median age: 48.8 – 54 years) is known to be 0.05 % – 0.07 % [3] [4].

In 2006, 57.1 % of US men and women aged 50 years or older reported they had undergone at least one examination with flexible sigmoidoscopy or colonoscopy [5]. Since about 55 000 000 US citizens have been “scoped,” on the basis of a prevalence rate of 0.05 % – 0.07 % one would expect some 27 500 – 38 500 rectal carcinoids to have been diagnosed “incidentally” by screening endoscopy in the United States. This is the reason why rectal carcinoids have recently attracted our attention.

Due to a lack of controlled prospective studies, the management of rectal carcinoids is a matter of debate. In this report the retrospective data from large national registries and large hospital series are reviewed.

As concerns nomenclature, (well-differentiated) neuroendocrine neoplasms of the rectum that either show angioinvasion or infiltration of the muscularis propria (or beyond) or have metastasized are called neuroendocrine carcinomas. The term “rectal carcinoid” does not distinguish between well-differentiated neuroendocrine carcinoma and well-differentiated neuroendocrine tumor (of the rectum); it comprises both [6].

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