Triple negative breast cancer gets positive news: KEYNOTE-522 interim results

Immunotherapy added to chemotherapy improves pathological complete response in patients with early triple-negative breast cancer, according to late-breaking results from the KEYNOTE-522 trial presented by Prof. Peter Schmid (Queen Mary University of London, UK) [1]. Interim results from the study, which is the first phase 3 trial of immunotherapy in early breast cancer, also indicated an improvement in event-free survival.

KEYNOTE-522 tested whether adding immunotherapy to chemotherapy prior to surgery could improve pathological complete response and event-free survival in women with early triple-negative breast cancer. A total of 1,174 patients were randomly allocated at a 2:1 ratio to pembrolizumab or placebo, both added to preoperative chemotherapy with anthracyclines, taxanes, and platinum for 5-6 months. After surgery, patients continued their allocated treatment of pembrolizumab or placebo for 9 cycles.

The analysis presented was performed after a median follow-up of 15.5 months. Pathological complete response, assessed in the first 602 patients, significantly increased from 51.2% (95% CI 44.1–58.3) in the placebo group to 64.8% (95% CI 59.9–69.5) in the pembrolizumab group (P=0.00055). These data indicate a 13.6% clinical benefit.

Because triple-negative breast cancer is aggressive and recurrences often occur early on, the investigators conducted an interim analysis of event-free survival. There was a favourable trend for the pembrolizumab group with a hazard ratio of 0.63 (95% CI 0.43–0.93), Prof. Schmid said. “These are preliminary data, but they provide a strong sign that the addition of immunotherapy to neoadjuvant chemotherapy prevents breast cancer recurrence. If we prevent recurrence, we cure more patients, but we need longer-term data for confirmation.”

Grade 3 or higher treatment-related adverse events occurred in 78.0% and 73.0% of the pembrolizumab and placebo groups, respectively. Prof. Schmid noted that many of the side-effects were driven by the intensive chemotherapy regimen. Side-effects with a potential link to immunotherapy occurred in 42% of study participants taking pembrolizumab versus 21% on placebo.

1. Schmid P et al. KEYNOTE-522: Phase 3 study of pembrolizumab (pembro) + chemotherapy (chemo) vs placebo (pbo) + chemo as neoadjuvant treatment, followed by pembro vs pbo as adjuvant treatment for early triple-negative breast cancer (TNBC). ESMO Congress 2019, 27 Sept-1 October 2019, Barcelona, Catalonia, Spain, Abstract LBA8_PR.

Posted on 26 November 201918 March 2021