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RE Sargent, E Vazquez, I Kang, J Lu, M Manchandia, P Sheth, A Terando, M Nelson, A Carr, SF Sener
LAC+USC/Keck School of Medicine

Previous research demonstrated that for breast cancer patients having diagnostic MRI after neoadjuvant chemotherapy (NAC), the false-negative rate for those having a radiographic complete response (rCR) to treatment was 27%. The accuracy of MRI in predicting pathologic complete response (pCR) after NAC was not sufficient to obviate the need for tissue diagnosis to assess for residual cancer. This study was designed to assess whether rCR and pCR were prognostic factors associated with relapse-free survival (RFS).

A single-institution retrospective analysis was performed including clinical, radiographic, and pathologic parameters for all breast cancer patients treated with NAC from 2015-2018, all of whom had pre- and post-NAC MRI. rCR after NAC was defined as the absence of suspicious MRI findings in the ipsilateral breast or nodes. pCR was defined as absence of invasive cancer or DCIS in breast or nodes after operation (ypT0N0M0). Univariable and multivariable analyses were performed. Kaplan-Meier method was used with log-rank test to evaluate differences in time-to-event distributions. Cox proportional hazards model included covariates in analyses.

For 102 patients, median follow-up was 43.5 months, the median survival was 62 months, and the five-year relapse-free survival (RFS) was 62%. The 41 (40%) patients who achieved pCR after NAC had a significantly higher five-year RFS than the 61 not achieving pCR (84.4% vs 51.2%, HR 0.368 (95%CI: 0.138-0.985), p=0.038). There was insufficient power to establish whether pCR was a prognostic factor for molecular subtypes of cancer, such as triple-negative or HER2+. The 44 (43%) patients who achieved a rCR after NAC had a similar five-year RFS to the 58 (57%) not achieving a rCR (64.0% vs 59.0%, HR 0.624 (95%CI: 0.268-1.455), p=0.27).

Pathologic response to NAC was a prognostic factor associated with relapse-free survival, but MRI response to NAC was not a prognostic factor. Results achieved at a large, urban safety net medical center were similar to those reported in randomized clinical trials.

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