Abstract: Small intestinal carcinoids (SIC) are the most common small bowel malignancies. We sought to determine the risk of developing SIC before and after other primary malignancies (PM) and the prognosis of patients with SIC, with and without another PM. We used the SEER database was used to identify patients diagnosed with SICs between 1973-2007. Multiple primary-standardized incidence ratios were calculated as an approximation of relative risk (RR) to explore the association of SICs with metachronous malignancies. Survival analysis was performed using Kaplan-Meier methods and Cox proportional-hazard models. Among 8,331 patients with SICs, 2,424 (29%) had another PM at some time. The most common sites were prostate (26.2%), breast (14.3%), colon (9.1%), lung/bronchus (6.3%), and bladder (5.3%). 67% had a PM diagnosed before the SIC (pre-SIC), 33% after (post-SIC), and 8% had a PM both before and after SIC. Among the pre-SIC group, the risk of future SIC was increased after cancers of the small bowel (RR11.86[95%CI6.13-20.72]), esophagus (4.05[1.10-10.36]), colon (1.39[1.05-1.81]), kidney (1.93[1.12-3.09]), prostate (1.38[1.17-1.62]), and leukemia (2.15[1.18-3.61]). Among the post-SIC group, there was an increased risk of future PM of the small bowel (8.78[4.54-15.34]), liver (2.49[1.08-4.91]), prostate (1.25[1.0-1.53]), and thyroid (2.73[1.10-5.62]). Compared to patients with only SIC, those with a PM pre-SIC had worse mean survival (57.9vs.40.9 months, HR1.55[1.42-1.69],p<0.001). In conclusion, almost one-third of patients with SICs have an associated metachronous primary tumor. When these primaries occur prior to (but not after) the SIC diagnosis, the prognosis is worse than with an initial SIC. The type of malignancies associated with SICs may guide future screening efforts.
Source: S Amin, Internal Medicine, Mount Sinai School of Medicine, New York, United States.