Complete response on MR imaging after neoadjuvant chemotherapy in breast cancer patients: Factors of radiologic-pathologic discordance

To evaluate the radiologic and clinicopathologic factors in radiologic-pathologic discordance (false-negative results) in breast cancer patients who demonstrate radiologic complete response (rCR) in MR imaging after neoadjuvant chemotherapy (NAC).Our institutional review board approved this retrospective study. We included 209 consecutive patients who showed rCR in MR imaging after NAC. rCR was diagnosed when the original lesion site showed no enhancement. Pathologic CR (pCR) was defined as the complete absence of both invasive cancer and ductal carcinoma in situ in the breast upon pathology. Clinicopathologic and radiologic factors affecting the radiologic-pathologic correlation were analyzed.pCR was noted in 108 patients (51.7%); the remaining 101 (48.3%) had residual lesion on pathology. False negative rCR findings were significantly more frequent in cases of 1 or 2 histologic grade (p = 0.001), low tumor-infiltrating lymphocytes (p = 0.004), and luminal A or B subtype (p 0.001). Multivariate analysis of radiologic findings to identify predictors of false negative findings found calcifications in mammography (p = 0.037), multifocal multicentric lesions (p = 0.004), and non-mass enhancement in pretreatment MR imaging (p = 0.023) to be significantly associated with false-negative findings.Patients with calcification in mammography, multifocal multicentric lesions, and non-mass enhancement in pretreatment MR imaging are significantly associated with false-negative results who showed rCR on MR imaging after NAC. These patient populations should be interpreted with caution.