Background: 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.
Methods: Seventy rectal carcinoid patients 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 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 (> or =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.
Conclusions: 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.