Posted: Monday, November 14, 2022
The combination of radiotherapy plus pembrolizumab given preoperatively may prove to be of benefit for some patients with early-stage triple-negative breast cancer, according to a phase Ib/II trial presented at the 2022 Society for Immunotherapy of Cancer (SITC) Annual Meeting (Abstract 644). “For the first time to our knowledge, a major pathologic response was observed in triple-negative breast cancer after a single radiotherapy plus pembrolizumab infusion,” said Julia Tchou, MD, PhD, of the University of Pennsylvania, Wayne, and colleagues. “Results of this proof-of-concept study may provide the rationale to evaluate the effectiveness of de-escalating preoperative combination immunotherapy in select patients in future studies,” she added.
The study was conducted in two phases and included three arms. In the first phase, six patients with triple-negative breast cancer were included in two of the arms. The first arm included four patients who received radiotherapy followed by pembrolizumab prior to surgery. The second arm included two patients who underwent pembrolizumab treatment and radiotherapy prior to surgery. None of the six patients in the first phase experienced a surgical delay or significant skin toxicity.
The second phase of the study was expanded to include a third arm in which patients with triple-negative breast cancer received pembrolizumab alone. Results from the third phase revealed that a significant increase in tumor-infiltrating lymphocytes occurred in patients with triple-negative breast cancer after treatment. In addition, the authors reported a major pathologic response (defined as less than 10% residual invasive tumor in post-treatment resected tissue) in three of nine patients included in the first two arms. One patient achieved a complete pathologic response. Although the authors recognized the cohort included in the study is small, they believe the trial establishes a basis to continue exploring a de-escalating preoperative combination immunotherapy.
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