Low dose DTIC is effective and safe in pretreated patients with well differentiated neuroendocrine tumors

Abstract

Background: Streptozocin (STZ) based chemotherapy is recommended for patients with metastatic pancreatic neuroendocrine tumors (pNET). Temozolomide as mono- or combination therapy has been suggested to be a promising alternative. However, the treatment is costly and not approved for the treatment of pNETs. Dacarbazine (DTIC) shares the active metabolite with temozolomide and is broadly available at a low cost. The aim of this study was a retrospective evaluation of the efficacy and tolerability of a lower dose DTIC-regimen in patients with progressive advanced NETs. Methods: We retrospectively analyzed 75 patients with NETs predominantly of pancreatic origin treated at our center between 1998 and 2013. 650mg/m2 of DTIC were administered intravenously over 60min every 4weeks. Morphological response was assessed according to RECIST1.1 criteria. The median progression free survival (PFS) was calculated using Kaplan-Meier and Cox regression methods, respectively. Univariate analyses of possible prognostic markers were performed. Results: The objective response rate (ORR) was 27% for the entire cohort and 32% in 50 pNET patients, respectively. Stable disease (SD) was documented in 29 patients (39%). Median PFS (mPFS) in patients receiving DTIC was 7months (3.9-10; 95% confidence interval). Radiological and biochemical response were the only significant prognostic markers for longer PFS in univariate analysis. Treatment was well tolerated. Nausea was the most common side effect (31%), only one case (1.3%) of grade 3 toxicity (vomiting) occurred. Conclusion: Low dose DTIC chemotherapy is an effective and well-tolerated treatment option in patients with progressive well differentiated neuroendocrine neoplasms, especially of pancreatic origin.