Triple-Negative Breast Cancer: Early Assessment with 18F-FDG PET/CT During Neoadjuvant Chemotherapy Identifies Patients Who Are Unlikely to Achieve a Pathologic Complete Response and Are at a High Risk of Early Relapse

Triple-negative breast cancer, an aggressive subtype, represents 15% of invasive breast tumors. This prospective study investigated whether early changes in 18F-FDG tumor uptake during neoadjuvant chemotherapy (NAC) can predict outcomes. Methods: Twenty (M0) patients underwent 18F-FDG PET/CT at baseline and after the second cycle. NAC was continued irrespective of PET results. Results: At surgery, 6 patients had a pathologic complete response, whereas 14 had residual tumor. Four patients showed early relapse (in the 2 y after surgery). There were 11 metabolic responders and 9 nonresponders using a 42% decrease in maximum standardized uptake value as a cutoff. In nonresponding patients, the risk of residual tumor at surgery was 100% (vs. 45% in responders; P = 0.014), and the risk of early relapse was 44% (vs. 0%; P = 0.024). Conclusion: A less than 42% decrease in 18F-FDG uptake at 2 cycles means residual tumor at the end of NAC and a high risk of early relapse.