MHC-II expression may predict anti-PD-1 pathway response in HER2-negative breast cancer
medwireNews: A major histocompatibility complex (MHC)-II tumor cell expression rate of 5% or more could identify HER2-negative breast cancer patients likely to benefit from the addition of PD-1 or PD-L1 inhibitors to standard neoadjuvant chemotherapy, research findings suggest.
The researchers analyzed tissue samples from 48 patients with early-stage triple-negative breast cancer treated with durvalumab and standard chemotherapy, 153 with HER2-negative breast cancer who received chemotherapy with or without pembrolizumab, and 381 HER2-negative patients who did not receive immunotherapy.
They used a predefined cutoff of 5% tumor cell positivity, which has been shown to predict benefit to anti-PD-1 monotherapy in patients with melanoma.
Area under the receiver operating characteristic curve analysis showed that this cutoff could distinguish between patients who were or were not likely to achieve a pathologic complete response with the addition of durvalumab or pembrolizumab to chemotherapy on 71% and 73% of occasions, respectively.
But this threshold did not predict response to chemotherapy alone, giving it “strong candidacy as a specific biomarker,” say Kim Blenman (Yale University School of Medicine, New Haven, Connecticut, USA) and co-workers.
They therefore conclude in Clinical Cancer Research: “These data suggest that tumor-specific MHC-II is an important, potentially pan-cancer, biomarker, which can be measured easily by tissue analyses, including standard [immunohistochemistry], that should be included in correlative analyses in future breast cancer immunotherapy Phase II and III trials.”
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