Radiotherapy in Combo With Chemo and Immunotherapy in Patients With PD-L1 Positive Metastatic TNBC

Patients with locally advanced unresectable or metastatic PD-L1 positive TNBC will be treated with radiation to one-four sites of metastasis amenable to radiation (sites of disease to be selected at the discretion of the treating radiation oncologist) followed by initiation of systemic therapy with pembrolizumab plus nab-paclitaxel/paclitaxel. Patients will be treated with pembrolizumab plus nab-paclitaxel/paclitaxel within 7 days of completion of radiation. Repeat imaging of all sites of disease will be performed every 9 weeks and response will be assessed according to RECIST 1.1. This is a two-stage, single-arm phase II study. Utilizing time-to-event outcomes, the investigators assumed an uninteresting 1-year PFS rate of 39% and a positive 1-year PFS rate of 60%. The first stage will enroll 17 subjects, with an additional 12 subjects to be enrolled in stage 2 if the trial is not stopped due to futility, for a total of 29 subjects. Enrollment will not be paused after the first stage of enrollment. At the time of the interim analysis the investigators would expect approximately 12 patients to have completed 1-year follow-up.