Colon and Rectal Neuroendocrine Tumors: Are They Really One Disease? A Single-Institution Experience over 15 Years.

Colon and rectal neuroendocrine tumors (NETs) are often studied as one entity. Recent evidence suggests that worse outcomes are associated with colon compared with rectal NETs; direct comparisons are lacking. Our aim was to assess clinicopathologic, treatment, and survival differences between these diseases. All patients who underwent resection of colorectal NETs at one institution from 2000 to 2014 were included and analyzed. Of 29 patients, 12(41%) had colon and 17 (59%) had rectal NETs. Baseline demographics were similar between groups, although colon patients tended to be symptomatic at presentation (67% vs 44%, P = 0.41). Eighty-three per cent of colon patients underwent surgical resection, whereas 77 per cent of rectal patients underwent endoscopic or transanal resection (P = 0.003). Colon patients had larger (3.4 cm vs 0.7 cm, P = 0.03), higher T-stage (T3/T4: 91% vs 14%, P = 0.003), higher grade tumors (42% vs 12%, P = 0.09) with more lymph nodes (58% vs 24%, P = 0.12) and lymphovascular invasion positivity (58% vs 24%, P = 0.32). Five-year disease-specific survival was 53% versus 80 per cent for colon and rectal patients, respectively (P = 0.22). After excluding high-grade tumors, colon NETs were associated with lymphovascular invasion positivity (100% vs 17%, P = 0.05) and advanced T-stage (80% vs 8%, P = 0.01). Colon and rectal 5-year disease-specific survival was 67 versus 80 per cent (P = 0.86). Colon and rectal NETs clinically seem to be distinct entities. Colon tumors have more aggressive clinicopathologic features, which may translate to worse outcomes. These differences in tumor biology may demand distinct management and should be further studied in a multi-institutional setting.