P-300 - Retrospective clinicopathological analysis of colon and rectal neuroendocrine tumors

Abstract

Introduction: Colorectal cancer is the second most common cause of cancer death after gastric cancer in Uzbekistan. A little number of colorectal neoplasms made up by neuroendocrine tumors (NET). Neuroendocrine tumors of the colon and rectum represent a broad clinical-pathologic spectrum with varying morphologic features and biological behavior. The aim of present study is to analyze pathological and clinical features of NET which have not been studied in Uzbekistan before. Methods: Study included 54 patients with colorectal NEN who were treated in National Cancer Research Center, between 2006 and 2011. In total, 36 (66.7%) patients were men and 18 (33.3%) were women, with a mean age of 56.4 years. The collected clinicopathological data were: patients' age, sex, tumor size, tumor location, pathological diagnosis based on WHO 2010 criteria, depth of tumor invasion, mitotic index [<2/10 high power fields (HPF), 220/10 HPF, or >20/10 HPF], Ki-67 labeling index (≤2, 320, or >20%), responses to treatment (operative procedure, chemotherapy or radiotherapy), metastases, and survival. Results: Tumor located in the rectum was observed in 44 (81.5%) cases, in 2 (3.7%) cases tumor was found in colon, and 8 (14.8%) patients had tumor in appendix. Morphologically, NET G1 – 30 (55.6%) cases, G2 – 12 (22.2%) cases, NEC (G3) – 8 (14.8%), and mixed adeno-neuroendocrine carcinoma (MANEC) was found in 4 (7.4%) cases. Of 54 patients, 18 underwent mucosectomy, and 36 were surgically resected with lymph node dissection. As for tumor size, the mean size was 21.7 mm, and 21 tumors (38.9%) were smaller than 10 mm. Most tumors were limited within mucosa or submucosa (44 cases, 81.5%), showed mitosis in <2/10 HPF (41 cases, 75.9%), and had a Ki-67 index of ≤2% (38 cases, 70.4%). Compared with rectal NENs, colonic NENs more frequently exhibited larger tumor size (P < 0.0001) and distant metastasis (P < 0.0001). Colonic NENs had a worse prognosis (P = 0.0027), with 5-year overall survival rates of 66.7% versus 88.1%. NET, NEC, and MANEC were noted in 61.8%, 23.5%, and 14.7% of patients, respectively. Palliative chemotherapy or radiotherapy did not improve survival rates in patients, who had distant metastasis at the time of diagnosis. However, noticed improvement in patients condition with stage IIA rectal small cell neuroendocrine carcinoma whom administered adjuvant chemotherapy with cisplatin and etoposide at our hospital. Conclusion: Retrospective analysis indicated that tumor size and pathological classification were associated with the prognosis. The worse outcome of colonic NENs observed in clinical practice might be due to not only to biological differences, but also to larger tumor size in colonic NENs. Surgical treatment remains major approach in NENs' therapy, whereas aggressive adjuvant chemotherapy with cisplatin and etoposide might offer a better chance of long-term survival for patients with stage II neuroendocrine carcinomas in the colon and rectum, which deserves further investigation.