Phase I/II study of streptozocin monotherapy in Japanese patients with unresectable or metastatic gastroenteropancreatic neuroendocrine tumors

Abstract

Background: This phase I/II study was conducted to evaluate the efficacy, safety and pharmacokinetics of streptozocin (STZ) in Japanese patients with unresectable or metastatic gastroenteropancreatic neuroendocrine tumors.

Methods: Twenty-two patients received up to 4 cycles of intravenous STZ at either 500 mg/m2 once daily for 5 consecutive days every 6 weeks (daily regimen) or at 1000-1500 mg/m2 once weekly for 6 weeks (weekly regimen). Tumor response was evaluated using the modified RECIST criteria ver. 1.1, and adverse events were assessed by grade according to the National Cancer Institute CTCAE (ver. 4.0).

Results: Fourteen (63.6%) patients completed the study protocol. No patients had complete response; partial response in 2 (9.1%), stable disease in 17 (77.3%), non-complete response/non-progressive disease in 2 (9.1%) and only 1 (4.5%) had non-evaluable disease. Excluding the latter, the response rate in the daily and weekly regimens was 6.7% (1/15) and 16.7% (1/6), respectively, with an overall response rate of 9.5% (2/21). However, the best overall response in each patient showed that the disease control rate was 100%.Adverse events occurred in all 22 patients, including 17 grade 3 adverse events in 11 patients; however, no grade 4 or 5 adverse events were reported. Prophylactic hydration and antiemetic treatment reduced the severity and incidence of nephrotoxicity, nausea and vomiting. Plasma STZ concentrations decreased rapidly after termination of infusion, with a half-life of 32-40 min. Neither repeated administration nor dose increases affected pharmacokinetic parameters.

Conclusions: STZ may be a useful option for Japanese patients with unresectable or metastatic gastroenteropancreatic neuroendocrine tumors.

Keywords: disease control; neuroendocrine tumor; streptozocin; tumor shrinkage.

Figure 1

A trial profile showing the number of patients enrolled, the number of patients who received the daily and weekly regimens, the number of patients who discontinued and the number of patients who remained in the study. STZ, streptozocin.

Figure 2

A waterfall plot of changes in tumor size from baseline in the STZ-naïve patients (14 in the daily regimen and 3 in the weekly regimen). Shaded bars represent patients receiving the weekly regimen.

Figure 3

Plasma concentration of STZ in patients after intravenous infusion.