Carcinoid of the Rectum Risk Stratification (CaRRs): A Strategy for Preoperative Outcome Assessment

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Abstract
Predicting rectal carcinoid behavior based exclusively on tumor size is imprecise. We sought to identify factors associated with outcome and incorporate them into a pre-operative risk stratification scheme. Seventy rectal carcinoid patients evaluated at our institution were identified. Demographic, clinical, and histopathologic data were collected and correlated with recurrence and survival. The mean age of our cohort was 53.6 years. Fifty-seven percent of patients were female. The mean tumor size was 1.3 cm (range: 0.1–5 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 elevated mitotic rate (≥2/50 HPF). Eleven patients (17%) had distant metastases at presentation. Sixty-one patients were followed for a median of 22 months (2–308 months), during which seven patients developed recurrence and seven died of disease (2/7 who developed recurrence). Poor outcome was associated with large tumor size, deep invasion, presence of LVI, and elevated 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. Poor prognostic features of rectal carcinoids include: large size, deep invasion, LVI, and elevated mitotic rate. The CaRRS score incorporates these features and accurately predicts outcome. Because the CaRRS score is based upon values available on pre-operative biopsy, it can identify patients with very favorable prognosis as well as those with poor prognosis that may benefit from additional staging or surveillance.