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February 16, 2009

Local Therapy of Rectal Carcinoids: A Matter of Debate

Arch Surg. 2009;144(2):193-197. doi:10.1001/archsurg.2008.542

Local therapy of small rectal carcinoids (<2 cm) is a matter of debate. The excellent article by Kwaan et al,1 recently published in the Archives, highlights this important issue.

Rectal carcinoids smaller than 2 cm have been and are being managed differently in different parts of the world.1-9 Owing to a lack of controlled prospective studies, our current management of rectal carcinoids is flawed by a low level of evidence. The best we can do for the time being is to base guidelines and recommendations on all the available (retrospective) data from case series, large hospital registries, and national tumor registries. Of course, the individual patient's situation has to be considered too. A 20-mm, well-differentiated rectal carcinoid may well be managed differently in a fit, otherwise healthy 32-year-old woman than in an 85-year-old multimorbid patient.

With respect to carcinoid tumor biology, even very experienced clinicians from different countries appear to favor different concepts.2,4-6 Nevertheless, a great body of evidence shows that rectal carcinoids 1 cm or smaller metastasize in 3% to 10% of patients,1-11 whereas rectal carcinoids 10.1 to 20 mm in diameter spread to regional lymph nodes in 17% to 42% of patients.1-12 The risk of lymph node metastases of rectal carcinoids is not lower than the metastatic risk of rectal adenocarcinoma.3,6-8,12 The prognoses in patients with metastatic rectal carcinoid disease are not better than those in patients with metastatic rectal adenocarcinoma.5-9,12 To stage localized rectal adenocarcinoma, physicians now advise patients to undergo pelvic nuclear magnetic resonance imaging and endoscopic ultrasonography (in nonstenotic cancer). In contrast to the standard of care in rectal adenocarcinoma, we use endoscopic ultrasonography and/or pelvic nuclear magnetic resonance imaging in surprisingly few patients with rectal carcinoids.1 Considering that lymph nodes are involved in as many as 17% to 42% of 1- to 2-cm rectal carcinoids,1,3,6-9,12 we must determine the stage of the carcinoid before deciding on treatment. Staging of localized rectal carcinoids should comprise endoscopic ultrasonography, pelvic nuclear magnetic resonance imaging (or pelvic computed tomography), and somatostatin-receptor scintigraphy.

Long-term Survival Data

Japanese tumor registries3,6 do report more favorable 5-year survival rates in patients with rectal carcinoids than registries from other parts of the world. In Japanese hospitals, rectal carcinoids larger than 10 mm are treated surgically, similar to adenocarcinomas.7 Lymph node dissection is considered standard of care for 10.1- to 20.0-mm rectal carcinoids. Small rectal carcinoids (≤1 cm) that exhibit lymphovascular invasion or infiltration of the muscularis propria or that have spread to locoregional lymph nodes are managed similarly.13 When evaluating different treatment strategies of well-differentiated (neuro)endocrine tumors, we have learned from such diseases as well-differentiated thyroid cancer that 10-, 15-, or even 20-year survival is a much more reliable and valid parameter than 5-year survival. Owing to the low aggressiveness of well-differentiated (neuro)endocrine tumors, even patients who will finally succumb to metastatic rectal carcinoid disease generally survive for the first 5 years.1,9 Kwaan et al1 point out that metastatic disease may not become clinically apparent for as long as 5 to 13 years after local therapy of a small (<10 mm), well-differentiated rectal carcinoid.

Thus, the 10-year survival rates of patients with rectal neuroendocrine tumors from not only the Surveillance, Epidemiology, and End Results registry of the National Cancer Institute but also the Japanese registries (Multi-Institutional Registry of Large Bowel Cancer and the Niigata database) should be published.3,6,11 Similarly, 10-year survival rates from European databases have to be reported. Thanks to Dr Irvin Modlin’s4,5,11 commitment, 10-year survival data of patients with carcinoid disease in the United States will be available this year.

Rectal Carcinoids 1 cm or Smaller

A broad consensus exists for the management of small (≤10 mm), well-differentiated rectal carcinoids that do not show lymphovascular invasion or infiltration of the muscularis propria or lymph node metastases. Such small, well-differentiated neuroendocrine tumors of the rectum can be managed by local excision performed either endoscopically or surgically.2,5,6,13-16 Before embarking on resection, the exact tumor size and in particular the depth of invasion has to be determined by endoscopic ultrasonography. Because more than 75% of rectal carcinoids infiltrate the submucosa, Sakata et al17 modified the ligation device (for esophageal varices) for use in the rectum, whereas Onozato et al18 optimized endoscopic submucosal dissection. By applying the latter techniques, both groups achieved complete resection of small rectal carcinoids in all of their patients.17,18 By omitting endoscopic ultrasonography in tumor staging and using conventional endoscopic techniques, indeterminate or even disease-positive resection margins (on histological examination) were observed in as many as 67% to 83% of patients.1,10 Obviously, endoscopic ultrasonography should precede local resection of rectal carcinoids. A thorough histologic workup of resected rectal carcinoids is important. As Shinohara et al13 and Kwaan et al1 point out, well-differentiated rectal carcinoids exhibiting lymphovascular invasion or infiltration of the muscularis propria can spread to regional lymph nodes despite the primary tumor measuring less than 10 mm in diameter. Lymph node dissection has to be considered in patients with node-positive carcinoid disease.6,12 Local resection of any rectal carcinoid smaller than 2 cm, as stated by Ramage et al,2 may not be adequate in a young, otherwise healthy patient with node-positive disease. Prospective studies, including innovative (neo)adjuvant treatment strategies, should be envisaged for node-positive rectal carcinoids.19

Correspondence: Dr Scherübl, Klinik für Innere Medizin–Gastroenterologie und Gastrointestinale Onkologie Vivantes-Klinikum Am Urban, Dieffenbachstrasse 1, Berlin 10967, Germany (hans.scheruebl@vivantes.de).

Financial Disclosure: None reported.

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