Is pembrolizumab plus RT safe to administer in TNBC?

Combination treatment with pembrolizumab and adjuvant radiotherapy (RT) does not pose any serious risk to patients with triple-negative breast cancer (TNBC), showing no increase in radiation-related adverse events (AEs), a study has shown.

Eighty-nine patients with locally advanced TNBC were included in this monocentric retrospective study conducted at Institut Curie in Paris, France. Eligible participants were treated according to the KEYNOTE-522 protocol: neoadjuvant chemotherapy and immunotherapy, followed by surgery and adjuvant therapy, including RT with or without pembrolizumab.

The authors divided patients into those receiving concurrent RT and pembrolizumab (RT-P) and those receiving RT alone. Treatment tolerance was the primary endpoint, while overall survival and cancer-specific survival served as secondary endpoints.

Of the patients, 41 received RT alone and 48 RT-P, with a median follow-up of 16 months. Baseline characteristics did not significantly differ between groups, as did overall toxicity, except for grade 1 radiodermatitis, which occurred more frequently in the RT-P group (83.3 percent vs 43.9 percent).

No grade ≥3 toxicity events occurred, but two grade 1 pulmonary toxicity events were reported in the RT-P group. The mean heart dose was 1.8 Gy, without any cardiac toxicity attributed to RT.

“Adjuvant radiotherapy can be safely administered concurrently with pembrolizumab in TNBC patients without increasing radiation-related adverse events, supporting the continuation of systemic therapy in this high-risk population,” the authors said. “Nevertheless, larger prospective studies are needed to assess long-term toxicity.”