Core needle biopsy-derived breast cancer microtumors enable functional drug-response testing for precision oncology

To predict neoadjuvant chemotherapeutic outcomes, breast cancer organoids have been developed. However, low yields from small tissue specimens and the high cost of niche factor-enriched medium remain barriers to clinical translation. Here, breast cancer patient-derived microtumors (PDMs) from core needle biopsies and small tissue specimens were established using a modified culture protocol and an optimized fetal bovine serum (FBS)-based culture medium, achieving a 75% success rate (6 of 8 cases). PDM characteristics mostly agreed with the tissue origins, according to growth evaluation, histopathology, immunohistochemistry, and genetic profiling. As a proof of concept, PDMs were tested with neoadjuvant chemotherapy alongside the patients' treatment. Notably, the PDM results were positively correlated with the patient outcomes and were obtained within a clinically relevant time frame (∼2-3 weeks). Collectively, our protocol and FBS-based medium efficiently generate breast cancer PDMs from core needle biopsies and small tissue specimens, with promising potential to guide neoadjuvant chemotherapy decisions.