A prospective phase II study of combined androgen blockade in patients with androgen receptor-positive metastatic or locally advanced unresectable salivary gland carcinoma

Background: There is no standard first-line chemotherapy for recurrent/metastatic (RM) or unresectable locally advanced (LA) salivary gland carcinoma (SGC). Patients and methods: We conducted a single institution, open-label, single arm, phase II trial of combined androgen blockade (CAB) for androgen receptor (AR)-positive SGC. Leuprorelin acetate was administered subcutaneously at a dose of 3.75 mg every 4 weeks. Bicalutamide was administered orally at a daily dose of 80 mg. Patients were treated until progressive disease or unacceptable toxicities. Results: Thirty-six eligible patients were enrolled. Thirty-three patients had RM disease and three patients had LA disease. The pathological diagnoses were salivary duct carcinoma (34 patients, 94%) and adenocarcinoma, NOS (two patients, 6%). The best overall response rate was 41.7% [n = 15, 95% confidence interval (CI), 25.5%-59.2%], the clinical benefit rate was 75.0% (n = 27, 95% CI, 57.8%-87.9%). The median progression-free survival was 8.8 months (95% CI, 6.3-12.3 months) and the median overall survival was 30.5 months (95% CI, 16.8 months to not reached). Additional analyses between treatment outcomes and clinicopathological factors or biomarkers including AR positivity, human epidermal growth factor receptor 2 status, and its complex downstream signaling pathway gene mutations showed no statistically significant differences. Elevated grade 3 liver transaminases and increased serum creatinine were reported in two patients, respectively. Discontinuation of leuprorelin acetate or bicalutamide due to adverse event occurred in one patient. Conclusion: This study suggests that CAB has equivalent efficacy and less toxicity for patients with AR-positive RM or unresectable LA SGC compared with conventional chemotherapy, which warrants further study. Clinical Trial Registration: UMIN-CTR (http://www.umin.ac.jp/ctr/index-j.htm), identification number: UMIN000005703.