Efficacy of Moxifloxacin plus Treatment of Physician's Choice in Patients with Metastatic Breast Cancer.

LESSONS LEARNED: Moxifloxacin plus continuation of the previous treatment of physician's choice shows promising efficacy in patients with metastatic breast cancer. The addition of moxifloxacin shows well-tolerated toxicities. BACKGROUND: Recent studies have confirmed bacterial infection as an important contributor in cancer. Elimination of tumor-associated microbes may lead to a reduction in tumors and improved survival. Moxifloxacin is an orally administrated fourth-generation quinolone with broad-spectrum coverage against tumor-associated bacteria. METHODS: In this study, we assessed the efficacy and safety of moxifloxacin in combination with treatment of physician's choice (TPC) in patients with metastatic breast cancer (MBC). In this single-arm, phase II study, we recruited 30 patients with MBC who had a trend toward disease progression (stable disease [SD] with increased tumor size) during TPC before enrollment at Sun Yat-sen University Cancer Center between January 1 and July 30, 2018. Eligible patients were given moxifloxacin once daily at a dose of 400 mg from days 1 to 7 of a 28-day cycle, in addition to continuing to receive the therapy previously selected by their physicians. Tumor response was determined according to RECIST (version 1.1). Progression-free survival (PFS) was calculated using the Kaplan-Meier method. RESULTS: The concomitant use of moxifloxacin and previous TPC yielded a median PFS of 6.6 months (95% confidence interval [CI]: 4.0-9.1) and a 1-year PFS of 25.9% (95% CI: 10.0%-41.9%). Objective responses were achieved in seven (23.3%, 95% CI: 7.3%-39.4%) patients. The clinical benefit rate was 46.7% (95% CI: 27.7%-65.6%). No grade 4 adverse events (AEs) and four grade 3 AEs were observed, none of which were considered to have definite relation to moxifloxacin. CONCLUSION: The combination of moxifloxacin with previous TPC shows promising efficacy and well-tolerated toxicities in patients with MBC.