Treatment and outcomes of neuroendocrine malignancies (NEMs) of the rectum.

Abstract

594 Background: NEMs of the rectum are rare and standard therapy is not well defined. We sought to characterize the clinicopathologic features, locoregional, and systemic management of a series of rectal NEMs and correlated these with outcomes. Methods: Patients referred to the BC Cancer Agency with rectal NEMs between 2005-2011 were included. Well-differentiated tumors with a Ki67 ≤20% and/or mitotic count ≤ 20 per high power field were classified as neuroendocrine tumors (NETs) while poorly differentiated tumors with higher Ki67 and/or mitotic count were classified as neuroendocrine carcinomas (NECs). Results: Of 28 NEMs, 18 (64%) NETs, and 9 (36%) NECs were identified with a median age of 56 and 59, respectively. Of 15 patients with stage I-III NETs, 13 underwent local excision, 2 had a surgical resection and none received pelvic radiation. Univariate analysis demonstrated an association between tumor size (< 1cm, 1-2 cm, > 2cm) and T stage (χ2 = 10.7, p = 0.03). One of 15 NETs developed distant relapse 8.9 months after surgical resection of a T1bN1 tumor. Of 9 NECs, only 2 presented with stage I-III tumors and were treated with radiation (1) or surgery (1). One patient developed distant relapse 4.8 months after radiation. Among all NEMs, liver was the most common site of metastasis (n = 10) followed by bone (n = 3). Median overall survival was 46.5 and 4.8 months for NETs and NECs (p < 0.01), respectively. Conclusions: Rectal NEMs comprise a rare subgroup of rectal tumors and may be classified as NETs or NECs. NETs generally present with early stage disease and are associated with good outcomes with local excision and without pelvic radiation. Rectal NECs frequently present with advanced disease and are associated with poor outcomes.