Invited discussant Erica Michelle Stringer-Reasor, MD, Associate Professor of Medicine and Director of the Breast Cancer Program at the O’Neal Comprehensive Cancer Center, University of Alabama at Birmingham, said the exploratory analysis of KEYNOTE-522 established the value of using residual cancer burden (RCB) to assess prognosis and help guide treatment in early-stage triple-negative breast cancer. The study joins those within the I-SPY network in showing that RCB is “a more detailed biomarker” than pathologic complete response; therefore, its use should be expanded, she said.

Erica Michelle Stringer-Reasor, MD

Dr. Stringer-Reasor continued: “Event-free survival was strictly associated with RCB scores, and the addition of pembrolizumab to chemotherapy certainly lowered these scores. This translated into an improved overall event-free survival. However, clearly, those patients who had moderate to extensive residual disease had poor survival, even with the use of pembrolizumab,” she observed.

Emerging Questions

“How can we clinically think about further stratifying patients who are at high risk of recurrence who do not achieve a pathologic complete response,” asked Dr. Stringer-Reasor. “Should we start thinking about other strategies, such as circulating tumor DNA, to help us tailor therapy to reduce the likelihood of recurrence?”

The study also showed that patients with RCB-0 and RCB-1 experienced few recurrences. This finding raises another important question: Are additional therapies such as capecitabine and olaparib warranted in all patients after surgery or just those with high RCB scores? Dr. Stringer-Reasor reminded listeners that some patients experience immune-related side effects, which can be long term. Studies are underway to address whether additional therapies truly benefit patients with little residual cancer, she added. 

DISCLOSURE: Dr. Stringer-Reasor has reported financial relationships with Breast Cancer Index, Lilly, Mylan, AstraZeneca, Immunomedics, Lilly, Merck, Novartis, OncoSec, and Seattle Genetics.