Efficacy of topotecan in pretreated metastatic poorly differentiated extrapulmonary neuroendocrine carcinoma

Therapeutic options for metastatic poorly differentiated neuroendocrine carcinoma (NEC) after prior platinum-based chemotherapy are limited. Topotecan is an approved second-line chemotherapy for small cell lung cancer (SCLC). NEC is often considered to show a biological behavior similar to SCLC. The aim of this study was to analyze the efficacy of topotecan in pretreated metastatic NEC patients. We performed a retrospective analysis of all patients treated with topotecan for metastatic NEC who presented at our center between January 2005 and December 2014 (n = 30). All 30 patients had received at least a platinum and etoposide containing regimen as prior chemotherapy. Median proliferation rate (Ki67) was 80%. As best response to topotecan five patients showed a stable disease, two patients a partial remission, resulting in a disease control rate of 23%. Of the remaining 23 patients, 14 (47%) showed a progressive disease, nine (30%) died before radiologic response could be evaluated. Median progression-free (PFS) and overall survival (OS) after start of topotecan was 2.1 and 4.1 months, respectively. In the subgroup analysis, patients with unknown primary (vs. those with a known primary) showed a significantly prolonged PFS of 3.5 months (vs. 1.9, P = 0.0107) and OS of 6.7 months (vs. 2.6 months, P = 0.0168). Grade 3/4 hematotoxicity was observed in 60% of patients. Topotecan shows only moderate antitumor activity in metastatic NEC. Disease control rate is lower than reported for SCLC. However, antitumor activity of topotecan seems higher in patients with unknown primary.