Gastrointestinal (GI) carcinoids, considered to be endocrine neoplasms with relatively low levels of malignancy, have never been examined in large, statistically reliable series to determine their true aggressive behavior in the early stage of both minute (≤ 5 mm) or small (5.1–10.0 mm) tumors at a depth of invasion restricted to the mucosa and submucosa (sm carcinoids).
Of a total number of 1914 cases of GI sm carcinoids selected from the Niigata Registry, 1614 with the tumor size recorded on a millimeter scale were categorized in 5-mm size intervals and rates of metastases were calculated for those in each size category. Of statistical significance was confirmation that the rectum (n = 849), the stomach (n = 449), the duodenum (n = 349), and the jejunoileum (n = 149) were among the principal growth sites. The Kaplan–Meier method was used to calculate 5-year-survival rates (5YSRs) and a comparative study was undertaken.
GI sm carcinoids exhibited a metastasis rate of 16.4% (264 of 1614) as a whole and minute carcinoids (≤ 5 mm) revealed an unexpectedly high metastasis rate of 6.0% (24 of 399) on average, which ranged from 3.7% (8 of 216) in the rectum to 17.2% (5 of 29) in the jejunoileum. Small carcinoids measuring 5.1–10 mm also showed a high metastasis rate of 13.3% (90 of 675) on average, ranging from 9.6% (12 of 125) in the stomach to 41.2% (14 of 34) in the jejunoileum. The combined average metastasis rate for both minute and small carcinoids combined (≤ 10 mm) was as high as 10.6% (114 of 1074). The comparative study confirmed that, in both the stomach and the rectum, the metastasis rate of sm carcinoids was significantly higher than that for ordinary sm carcinomas in tumors > 10 mm. Although most patients (92.8%; 1777 of 1914) underwent an endoscopy and/or a wider resection of the lesions, nonresectable metastases were found in 22 patients (1.1%). Of these, 16 had undergone a laparotomy and 6 had not received surgery. Among 1001 patients with GI sm carcinoids, the 5YSRs after curative resection ranged from 98.3% in the rectum to 89.6% in the stomach (P < 0.05), representing an average of 96.7% for the entire series.
Unexpectedly high aggressiveness in metastasis rates in both rectal and gastric sm carcinoids > 10 mm exhibiting values significantly higher than those of sm carcinomas were found in 1914 patients suffering from GI sm carcinoids. However, in sm carcinoids at either the minute or small tumor stage (tumors ≦ 10 mm), the metastasis rates were comparable to those of sm carcinomas. It should be emphasized that the 5YSRs for patients with GI sm carcinoids may be comparable to those with sm carcinomas in certain cases. These points should be taken into consideration when treating patients with GI carcinoids, particularly in the early stage, and even with the depth of invasion confined to the submucosa. Cancer 2005. © 2005 American Cancer Society.