668 Background: Optimal management of rectal neuroendocrine tumors (NETs) is not well defined. We characterized the clinicopathologic features, loco-regional, and systemic management of a population-based cohort of rectal NETs. Methods: Patients diagnosed with rectal NETs from 1999-2011 were identified from British Columbia provincial databases. NETs were classified as G1 and G2 tumors with a Ki-67 ≤ 20% and/or mitotic count ≤ 20 per high power field. Results: Of 91 rectal NETs, median age was 58 (IQR 48-65) years and 35 (38%) were male. Median tumor size was 6 (IQR 4-8) mm. Median overall survival was 164.7 months, with 3 patients presenting with stage IV disease. Treatment included local excision (n = 79), surgical resection (n = 6), and pelvic radiation (n = 1; T3N1 tumor). Final margin status was positive in 17 (20%) cases. Local relapse occurred in 8 (9%) cases, and one relapse to bone 13 months after T3N1 tumor resection. Univariate analysis demonstrated an association between local relapse and T classification, Ki-67, mitotic count, grade, and perineural invasion (p< 0.01), but not N or M classification, or lymphovascular invasion. Local relapse was not associated with surgical management or margin status. Of 3 patients with metastatic disease, two received systemic management, with capecitabine and temozolomide. Conclusions: Rectal NETs generally presented with small, early tumors and were treated with local excision or surgical resection without pelvic radiation. [Table: see text]
PD46-10 RISK OF SECONDARY MALIGNANCIES AFTER PELVIC RADIATION: A POPULATION-BASED ANALYSIS
