Purpose: To investigate the value of using changes in three parameters (tumor size, transfer constant (K-trans), and rate constant (k(ep)) obtained after the first treatment-cycle in predicting the final clinical response after two to four cycles of neoadjuvant anthracycline and cyclophosphamide (AC) chemotherapy.
Materials and Methods: Early changes in the three parameters were measured in 29 patients with invasive breast cancer by MRI after one cycle of treatment. Changes were then assessed for their predictive value of final clinical response and compared among patients with four different response patterns, Group 1 = responder (R) after one cycle and also R after four cycles, Group 2 = nonresponder (NR) after one cycle, but eventual R after four cycles, Group 3 = NR after one cycle and still NR after four cycles, and Group 4 = NR after one cycle and determined as NR after two cycles, being switched to the taxane regimen.
Results: Pearson's correlation analysis revealed significant correlation between early changes in tumor size and both pharmacoldnetic parameters (r = 0.49 and P < 0.01 or K-trans, r = 0.66 and P < 0.001 for k(ep)). The areas under the receiver operating characteristic (ROC) curve differentiating between R (Groups 1+2) and NR (Groups 3+4) groups using changes in tumor size, K-trans, and k(e)p were 0.88 (standard error [SE] 0.06, P < 0.0001), 0.63 (SE = 0.11, P = 0.11), and 0.77 (SE = 0.09, P = 0.001), respectively.
Conclusion: Early tumor size change in MRI after one cycle is better response predictor than that of either K-trans. or k(ep) in breast cancer undergoing neoadjuvant chemotherapy using an AC regimen.