A Phase 1 Dose-Escalation Trial of Radiation Therapy and Concurrent Cisplatin for Stage II and III Triple-Negative Breast Cancer.

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Patients with triple-negative breast cancer (TNBC) experience higher local-regional recurrence rates than those with luminal or HER2-positive tumors. This prospective, phase 1B trial was designed to assess the safety and to establish the maximum tolerated dose (MTD) of cisplatin with radiation therapy for women with early-stage TNBC. Eligible patients had stage II or III TNBC. Cisplatin was initiated at 10 mg/m2 intravenously once weekly during radiation and then escalated in a 3 + 3 design by 10 mg/m2 at each dose level until 40 mg/m2, or the MTD, was reached. Patients undergoing breast-conserving therapy (BCT) or mastectomy were accrued in separate parallel cohorts during dose escalation, followed by a 10-patient expansion at the MTD. During 2013 to 2018, 55 patients were accrued. Four patients developed dose-limiting toxicity. In the BCT cohort, 1 patient receiving 40 mg/m2 developed tinnitus resulting in a cisplatin delay; therefore, this was the BCT cohort MTD. In the mastectomy cohort, 1 patient receiving 20 mg/m2 developed a grade 3 urinary infection, and 2 additional patients had dose-limiting toxicities at 40 mg/m2 (grade 3 neutropenia and grade 2 tinnitus), both resulting in cisplatin delay. Thus, 30 mg/m2 was the mastectomy cohort MTD. Median follow-up was 48.5 months. Three-year disease-free survival was 74.7% for the BCT cohort and 64.4% for the mastectomy cohort. Adjuvant radiation therapy with concurrent cisplatin is feasible with a recommended phase 2 dose of 30 mg/m2 and 40 mg/m2 intravenously weekly in mastectomy and BCT cohorts, respectively.