Early breast cancer response to neoadjuvant chemotherapy: Defining the optimal timing and response rate using clinical tumor measurement.

121 Background: Breast cancer pathological complete response (pCR) following neoadjuvant therapy (NAT) is associated with better survival in some tumor subtypes. There is interest in identifying methods to increase early prediction of pCR during NAT. A simple and inexpensive technique such as early clinical breast examination has been shown to correlate with pCR during NAT in some studies. However, the optimal timing of the measurement and the best tumor response (TR) rate to predict pCR still need to be defined. Methods: We conducted a retrospective cohort study of patients prospectively enrolled in the following NSABP trials in one academic center (Montreal, Canada): B-40, B-41, FB-AX-003, FB-4, FB-5 and FB-6. Patients with T4 disease or disease progression were excluded. Clinical tumor measurements were recorded before each cycle of NAT. TR was measured as the percentage decrease in the largest tumor diameter. ROC curves for TR measurements at each time point were generated, comparing areas under the c...