Endoscopically identified well-differentiated rectal carcinoid tumors: Impact of tumor size on the natural history and outcomes

Background There is a paucity of data pertaining to the natural history and outcomes of patients with well-differentiated rectal carcinoids. Objective To correlate endoscopic size with the natural history and outcome. Design Retrospective study. Setting Single tertiary referral center. Patients Eighty-seven patients with endoscopically identified well-differentiated rectal carcinoid tumors. Intervention Colonoscopy. Main Outcome Measurements Prevalence of metastasis at diagnosis, disease progression, and survival. Results Metastasis was present at diagnosis in 3%, 66%, and 73% of tumors measuring ≤10 mm, 11 to 19 mm, and ≥20 mm, respectively. Metastasis was predicted with 100% sensitivity and 87% specificity using an endoscopic lesion size ≥9 mm. In patients without identified metastasis, 64% were identified during screening colonoscopy. Within this select cohort, subsequent metastasis was discovered only at distant extra pelvic sites, in 1.6%, 50%, and 100% of patients with tumors initially measuring ≤10 mm, 11 to 19 mm, and ≥20 mm, respectively. The carcinoid related 5- and 10-year survival rates for locally confined disease were 96%. The corresponding survival rates for local and advanced metastatic disease were 60% and 35%, respectively. Limitations Subjective estimation of tumor size, mitotic index or Ki-67 labeling index not reported, and lack of formal and standardized baseline staging algorithm and surveillance program. Conclusions The clinical behavior of 11- to 19-mm tumors appears to mimic that of larger (>20 mm) lesions with respect to the presence of metastasis at diagnosis and disease progression. Therefore, if local therapy is contemplated, we propose to make a distinction between ≤10-mm and 11- to 19-mm tumors, favoring an aggressive staging and management protocol for 11- to 19-mm carcinoid tumors.