Streptozocin/5-fluorouracil chemotherapy is associated with durable response in patients with advanced pancreatic neuroendocrine tumours

Background The role of systemic chemotherapy for pancreatic neuroendocrine tumours (pNET) is controversially discussed. Objective response rates (RR) reported for streptozocin (STZ)-based chemotherapy are variable and novel targeted drugs have recently been approved. However, the sequence of treatment remains unclear. We aimed to evaluate the efficacy of STZ plus 5-fluorouracil (STZ/5-FU) in a large pNET cohort. Methods Data from 96 pNET patients treated with STZ/5-FU were analysed retrospectively. Endpoints of the study were RR, time to tumour progression (TTP) and overall survival (OS). Results Mean age of patients at the start of chemotherapy was 57.6 years (range, 32.1-80.4). STZ/5-FU was the 1st line treatment in 56.3%. 11.5% had G1, 79.2% G2 and 6.3% G3 neoplasms. Baseline progression was evident in 74%. Objective response rate was 42.7%. 40.6% of patients showed stable disease as best response while 16.7% showed progressive disease. Treatment was discontinued due to toxicity in 16 patients. Median TTP and OS were 19.4 (95% confidence interval (CI), 13.6-25.2) and 54.8 months (95% CI, 34.7-74.9), respectively. In Cox regression analysis, Ki67 > 15% was the only negative prognostic factor for TTP (hazard ratio (HR), 3.3; P < 0.001), confirmed by multivariate analysis (HR, 6.7; P = 0.001). Conclusions STZ/5-FU was associated with considerable RR. Treatment was associated with durable TTP especially in patients with Ki67-index of ≤15%. These findings along with good tolerability strengthen the value of this two-drug chemotherapy for the management of unresectable pNET.