FDA Approves Neoadjuvant Pembro for Triple-Negative Breast Cancer

Sharon Worcester


July 28, 2021

The US Food and Drug Administration (FDA) has approved the neoadjuvant use of pembrolizumab (Keytruda) in combination with chemotherapy for patients with high-risk early-stage triple-negative breast cancer (TNBC) and as single-agent adjuvant treatment to be continued after surgery.

This approval is based on findings from the randomized, phase 3 KEYNOTE-522 trial, which showed significantly prolonged event-free survival with the pembrolizumab regimen vs neoadjuvant chemotherapy alone for previously untreated stage II or III TNBC.

This is the 30th indication for pembrolizumab in the United States.

The immunotherapy received accelerated approval in November 2020 for adjuvant use in locally recurrent unresectable or metastatic TNBC for patients whose tumors express programmed cell death–ligand-1 (PD-L1), as determined by an FDA-approved test. That accelerated approval was based on results from the phase 3 KEYNOTE-355 trial. The approval has now been converted to a full approval on the basis of confirmatory data from the KEYNOTE-522, notes a statement from the manufacturer, Merck.

"Triple-negative is a difficult-to-treat type of breast cancer that unfortunately is more common in the US in younger women and in Black women," commented Vicki Goodman, MD, vice president of clinical research, Merck Research Laboratories. "We are proud to offer a new treatment option for patients faced with this challenging cancer. This neoadjuvant and adjuvant combination with pembrolizumab is the first immunotherapy regimen to be approved in high-risk early-stage TNBC, marking a meaningful milestone for the breast cancer community."

In the KEYNOTE-522 trial, participants were randomly assigned to receive either placebo or pembrolizumab plus chemotherapy with carboplatin and paclitaxel, followed by doxorubicin or epirubicin and cyclophosphamide before surgery, as well as placebo or pembrolizumab as single-agent therapy after surgery.

The results from this trial, first reported in 2019 at the annual meeting of the European Society of Medical Oncology, showed that for patients in the pembrolizumab arm of the trial, the pathologic complete response rate was nearly 65%, vs 51% among the patients who received placebo. The benefit was seen both in those whose tumors were positive and those whose tumors were negative for PD-L1 expression.

Among patients in the pembrolizumab arm, there was a 37% reduction in the risk for disease progression that precluded definitive surgery, a local/distant recurrence, a second primary cancer, or death from any cause (hazard ratio, 0.63).

Pembrolizumab can be associated with immune-mediated adverse reactions that may be severe or fatal, Merck notes.

These events "can occur in any organ system or tissue and can affect more than one body system simultaneously. Immune-mediated adverse reactions can occur at any time during or after treatment," Merck warns. The company states, "Early identification and management of immune-mediated adverse reactions are essential."

Treatment may need to be withheld or permanently discontinued, and corticosteroids may be needed, depending on the severity of the adverse reaction, according to the statement.

Infusion-related reactions can also occur. Because of its mechanism of action, pembrolizumab can cause fetal harm when administered to women during pregnancy.

Sharon Worcester is an award-winning medical journalist at MDedge News, part of the Medscape Professional Network.

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