Carcinoid of the rectum risk stratification (CaRRS): A strategy for preoperative outcome assessment

Background: Predicting rectal carcinoid behavior exclusively on the basis of tumor size is imprecise. We sought to identify factors associated with outcome and incorporate them into a preoperative risk stratification scheme. Methods: Seventy patients with rectal carcinoid evaluated at our institution were identified. Demographic, clinical, and histopathologic data were collected and correlated with recurrence and survival. Results: The mean age of our cohort was 53.6 years. Fifty-seven percent of patients were women. The mean tumor size was 1.3 cm (range, .1-5 cm). Twenty-five percent of patients had deeply invasive tumors (into the muscularis propria or deeper); an equal percentage had tumors with lymphovascular invasion (LVI) or an increased mitotic rate (two or more mitoses per 50 high-power fields). Eleven patients (17%) had distant metastases at presentation. Sixty-one patients were followed for a median of 22 months (range, 2-308 months), during which seven patients developed recurrence and seven died of disease (including two of seven whose disease recurred). Poor outcome was associated with large tumor size, deep invasion, presence of LVI, and increased mitotic rate. These factors were incorporated into a Carcinoid of the Rectum Risk Stratification (CaRRS) score. CaRRS predicted recurrence-free and disease-specific survival better than any single factor alone. Conclusions: Poor prognostic features of rectal carcinoids include large size, deep invasion, LVI, and increased mitotic rate. The CaRRS score incorporates these features and accurately predicts outcome. Because the CaRRS score is based on values available by preoperative biopsy, it can identify patients with favorable prognosis and those with poor prognosis who may benefit from additional staging or surveillance.