Pembrolizumab Improves 7-Year OS in Early-Stage TNBC: KEYNOTE-522 Final Data

At the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, updated results from the landmark phase 3 KEYNOTE-522 trial reaffirmed the role of neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab as a standard of care for patients with high-risk early-stage triple-negative breast cancer (TNBC). The final analysis, presented after a median follow-up of 93.8 months, demonstrates that the addition of the PD-1 inhibitor significantly improves both event-free survival (EFS) and overall survival (OS).

Unprecedented long-term survival

The study randomized 1,174 patients to receive either pembrolizumab plus chemotherapy or placebo plus chemotherapy in the neoadjuvant setting, followed by continued pembrolizumab or placebo after surgery. According to the latest data, the 7-year OS rate was 85.1% in the pembrolizumab group compared to 77.2% in the placebo group (HR, 0.64; 95% CI, 0.49-0.85).

The benefits were equally robust for EFS, with a 7-year rate of 78.3% for those receiving the immunotherapy combination versus 69.8% for those on chemotherapy alone (HR, 0.68; 95% CI, 0.54-0.86). These results remained consistent across key subgroups, including PD-L1 expression and nodal status.

Safety and nursing management

For oncology nurses, understanding the toxicity profile of this regimen is critical. In an interview prior to the meeting, Javier Cortes, MD, PhD, highlighted that the addition of pembrolizumab does not significantly exacerbate traditional chemotherapy side effects.

“We have to differentiate here the chemotherapy related adverse events which are very well known... Basically we have to deal with neutropenia. We have to deal of course with gastrointestinal adverse events basically nausea and vomiting,” Cortes explained. He noted that neurotoxicity associated with carboplatin and paclitaxel also remains a concern, but emphasized that these "most frequent adverse events... [are] not increased at all" by adding the immunotherapy.

However, the trial did show an increase in immune-mediated adverse events (35.0% in the pembrolizumab arm vs 13.1% in the placebo arm). Dr. Cortes provided specific guidance for clinical monitoring: “My advice here? First of all we should never forget about testing the thyroid function because hypo or hyperthyroidism is relatively frequent very easy to be managed but we have to follow up”.

In addition to thyroid monitoring, nurses should be vigilant for skin reactions, which Cortes estimated occur in approximately 5% to 6% of patients. He reassured clinicians that while monitoring is essential, severe complications are rare, stating that “grade four or of course grade five are very very very infrequent.”

The nearly 8-year follow-up from KEYNOTE-522 provides definitive evidence that the pembrolizumab-chemotherapy sequence provides a clinically meaningful survival advantage for high-risk TNBC. As this regimen continues to be utilized in clinics, the focus for nursing teams remains on the proactive management of immune-related side effects to ensure patients can complete the full course of therapy safely.

Reference

Cortes J, et al. Pembrolizumab and Long-Term Survival in High-Risk Early-Stage TNBC. Final analysis of KEYNOTE-522. Presented at: ASCO Annual Meeting; May 2026.