Circulating Tumor DNA Predicts the Response and Prognosis in Patients With Early Breast Cancer Receiving Neoadjuvant Chemotherapy

PURPOSE Many patients with breast cancer still relapse after curative treatment. How to identify the ones with high relapse risk remains a critical problem. Circulating tumor DNA (ctDNA) has recently become a promising marker to monitor tumor burden. Whether ctDNA can be used to predict the response and prognosis in patients with breast cancer receiving neoadjuvant chemotherapy (NAC) is unknown. Our study aimed to evaluate the clinical value of the presence and dynamic change of ctDNA to predict the tumor response and prognosis in patients with breast cancer treated with NAC. MATERIALS AND METHODS Fifty-two patients with early breast cancer who underwent NAC were prospectively enrolled. Serial plasma samples before, during, and after NAC and paired tumor biopsies were harvested and subjected to deep targeted sequencing using a large next-generation sequencing panel that covers 1,021 cancer-related genes. RESULTS Positive baseline ctDNA was detected in 21 of 44 patients before NAC. Most patients with positive ctDNA had one or more mutations confirmed in paired primary tumor. The ctDNA level after 2 cycles of NAC was predictive of local tumor response after all cycles of NAC (area under the curve, 0.81; 95% CI, 0.61 to 1.00). ctDNA tracking during NAC outperformed imaging in predicting the overall response to NAC. More importantly, positive baseline ctDNA is significantly associated with worse disease-free survival ( P = .011) and overall survival ( P = .004) in patients with early breast cancer, especially in estrogen receptor–negative patients. CONCLUSION Our study demonstrated that ctDNA can be used to predict tumor response to NAC and prognosis in early breast cancer, providing information to tailor an individual’s therapeutic regimen.