Symmans WF, Yau C, Chen YY, et al. - Considering the possible value of knowledge concerning residual cancer burden (RCB) distributions for improving the interpretation of efficacy in neoadjuvant breast cancer trials, researchers herein examined variation in the pattern of and prognosis for RCB after neoadjuvant chemotherapy for breast cancer by subtype and treatment.

• Analysis of data from I-SPY2, which is a multicenter, platform adaptive, randomized clinical trial in the US.

• Comparison of investigational agents in combination with chemotherapy was done with chemotherapy alone in adult women with stage 2/3 breast cancer at high risk of early recurrence.

• Included were 938 women (mean [SD] age, 49 [11] years; 66 [7%] Asian, 103 [11%] Black, and 750 [80%] White individuals) from the first 10 investigational agents, with a median follow-up of 52 months.

• There appeared significantly worsened event-free survival per unit of RCB in every subtype of breast cancer.

• Overall, findings suggest robust value of RCB after neoadjuvant chemotherapy as a prognostic response measure across treatments and within subtypes.

• A shift in the distribution of RCB along with increased pCR rate and an improved EFS appeared in correlation with providing effective neoadjuvant treatments.

• When compared between randomized treatments, RCB seemed to be a clinically useful measure of efficacy.