ESMO 2023: KEYNOTE-522 Update on Use of Pembrolizumab in Triple-Negative Breast Cancer

By: Celeste L. Dixon
Posted: Monday, November 6, 2023

In almost 1,200 patients with early-stage triple-negative breast cancer, neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab continued to show a clinically meaningful improvement in event-free survival compared with neoadjuvant chemotherapy alone, regardless of the pathologic complete response outcome, according to updated results from the phase III KEYNOTE-522 trial. These longer-term study data—event-free survival results after a median follow-up of about 5 years—were presented at the European Society for Medical Oncology (ESMO) Congress 2023 (Abstract LBA18) by Peter Schmid, MD, PhD, of Barts Breast Cancer Centre, London, and colleagues.

The eligible patients were those with previously untreated, nonmetastatic, centrally confirmed triple-negative breast cancer (stage T1c N1–2 or T2–4 N0–2). They were randomly assigned on a 2:1 basis to receive neoadjuvant pembrolizumab at 200 mg every 3 weeks (n = 784) or placebo (n = 390), both given with four cycles of paclitaxel plus carboplatin, then with four cycles of doxorubicin or epirubicin plus cyclophosphamide. The trial’s dual primary endpoints are pathologic complete response and event-free survival. After definitive surgery, patients received adjuvant pembrolizumab or placebo for nine cycles or until recurrence or unacceptable toxicity.

A total of 18.5% of the pembrolizumab group and 27.7% of the placebo group had an event-free survival event (hazard ratio [HR] = 0.63). The 60-month event-free survival rate was 81.3% vs 72.3%, respectively; the median was not reached in either group.

“With 210 distant events, the rate of distant disease progression or distant recurrence–free survival at 60 months was 84.4% with pembrolizumab vs 76.8% with placebo (HR = 0.64),” continued Dr. Schmid and co-investigators. “The event-free survival benefit with pembrolizumab was consistent across prespecified subgroups, including PD-L1 expression and nodal status.” Further, they reported, in a prespecified, nonrandomized, exploratory analysis, the 5-year event-free survival rates with and without pembrolizumab were 92.2% and 88.2%, respectively, in patients with a pathologic complete response, and 62.6% and 52.3% in patients without such a response.

Disclosure: The study authors’ disclosure information can be found at cslide.ctimeetingtech.com.

ESMO Congress 2023