Clinicopathologic features, treatment, prognosis and prognostic factors of neuroendocrine carcinoma of the endometrium: a retrospective analysis of 42 cases from the Kansai Clinical Oncology Group/Intergroup study in Japan

OBJECTIVE: We conducted a retrospective, multi-institutional, collaborative study to accumulate cases of neuroendocrine carcinoma of the endometrium, to clarify its clinicopathologic features, treatment, prognosis and prognostic factors to collate findings to establish future individualized treatment regimens. To our knowledge, this is the largest case study and the first study to statistically analyze the prognosis of this disease. METHODS: At medical institutions participating in the Kansai Clinical Oncology Group/Intergroup, cases diagnosed at a central pathologic review as neuroendocrine carcinoma of the endometrium between 1995 and 2014 were enrolled. We retrospectively analyzed the clinicopathologic features, treatment, prognosis and prognostic factors of this disease. RESULTS: A total of 65 cases were registered from 18 medical institutions in Japan. Of these, 42 (64.6%) cases were diagnosed as neuroendocrine carcinoma of the endometrium based on the central pathological review and thus included in the study. Advanced International Federation of Gynecology and Obstetrics stages (stage III and IV) and pure type small cell neuroendocrine carcinoma cases had a significantly worse prognosis. Upon multivariate analysis, only histologic subtypes and surgery were significant prognostic factors. Pure type cases had a significantly worse prognosis compared to mixed type cases and complete surgery cases had a significantly better prognosis compared to cases with no or incomplete surgery. CONCLUSION: Our findings suggest that complete surgery improves the prognosis of neuroendocrine carcinoma of the endometrium. Even among cases with advanced disease stages, if complete surgery is expected to be achieved, clinicians should consider curative surgery to improve the prognosis of neuroendocrine carcinoma of the endometrium.