Single-center study of prognostic relevance of patient-derived xenograft engraftment in newly diagnosed triple-negative breast cancer

Assessing risk of recurrence for nonmetastatic triple-negative breast cancer (TNBC) is a key determinant of therapeutic strategy. The best predictor of recurrence risk is failure to achieve a pathologic complete response after preoperative chemotherapy, but it imperfectly correlates with relapse-free an overall survival. The noninterventional TOWARDS study at the University of Utah (Salt Lake City) evaluated the prognostic relevance of patient-derived xenograft (PDX) engraftment into female NOD/SCID mice. Among 80 newly diagnosed TNBC patients there were 18 whose PDX engrafted. Relapse within one year was seen in 8 of 18 (44.4%) whose PDX engrafted versus 1 of 62 (1.6%) of patients whose tumors did not engraft (HR 17.5; p<0.001). HRs for overall survival an d breast cancer-specific survival in PDX+ patients were 21.1 (p<0.001) and 39.5 (p<0.001), respectively. The authors conclude that the ability of a tumor to engraft as a PDX predicts early recurrence.