Researchers at the University of California, San Francisco, have developed a laboratory-based method that could help predict how individual breast tumors respond to cancer treatment. The approach combines molecular data from the I-SPY2 breast cancer trial with patient-derived organoids—three-dimensional “mini tumors” grown from a patient’s own cancer cells. In early testing, these organoids reproduced treatment responses observed in the corresponding tumors and helped identify drug combinations that may overcome resistance, including resistance in aggressive triple-negative breast cancer. I-SPY2 is designed to accelerate the testing of therapies for high-risk breast cancer by evaluating several treatments simultaneously in biologically defined patient groups. With further validation in prospective clinical studies, patient-derived organoids could eventually become a practical bridge between molecular biomarkers and more individualized breast cancer treatment.