Nature: blood biomarker proposed to predict immunotherapy response in breast cancer

Nature describes work identifying a blood-measured biomarker intended to predict which patients with certain breast cancer types will respond to immunotherapy. The question matters clinically because checkpoint inhibitors benefit only a subset of patients and there is currently no reliable way to identify them in advance. The available note gives neither the name of the biomarker, nor the number of patients studied, nor any measure of test accuracy, so at this stage it is a research signal rather than a tool for practice — confirmation would require prospective studies in larger cohorts.