Is staging breast magnetic resonance imaging prompted upgrade to mastectomy appropriate?

BACKGROUND: Breast magnetic resonance imaging (MRI) use for surgical staging is increasing, though remains controversial. We aimed to evaluate the accuracy of MRI in surgical decision-making to determine if mastectomy prompted by MRI was appropriate. METHODS: A single-centre observational study in Perth, Western Australia, with the inclusion of all preoperative and postoperative studies (e.g. involved margins after breast-conserving surgery) undergoing staging breast MRI from 1 January 2015 to 26 August 2019. A standard protocol using gadolinium contrast was used. The reference standard was postoperative histopathology or, for studies without additional surgery after MRI following breast-conserving surgery, the next and subsequent annual screening episodes. By reviewing the final histopathology, the medical case notes and multidisciplinary team decision process, we evaluated whether the reported MRI disease extent was accurate in prompting an appropriate upgrade to mastectomy. Outcomes are reported with descriptive statistics. RESULTS: Of 130 cancers staged with MRI; seven were excluded as information was incomplete, 104 were performed preoperatively and 19 postoperatively. The majority (60%) staged lobular carcinoma (invasive 59%, in situ 1%) compared to ductal carcinoma (invasive 31%, in situ 8%). For preoperative MRI, half (54% - 56/104) underwent subsequent mastectomy. Of these, MRI prompted mastectomy in 45% (25/56), all appropriate for disease extent. In the postoperative staging group, two mastectomies were performed, one planned before imaging, the other prompted when MRI diagnosed residual disease and confirmed on histopathology. No false-negative staging MRI was identified. CONCLUSIONS: In our cohort, MRI prompted an upgrade to mastectomy in 21% (26/123), appropriate for cancer extent.

Does Medicare-eligible high-risk breast cancer screening MRI target the right women?

INTRODUCTION: MRI is the most sensitive modality to screen for breast cancer, but it is expensive with somewhat limited access. Audit of screening performance should reflect appropriate population targeting. METHODS: An observational study on consecutively screened high-risk women, assessment of the contralateral breast staging a new cancer, or surveillance in women with prior breast cancer or high-risk lesion in Perth, Western Australia. All breast MRI studies from 1 January 2015 to 7 September 2018 were included. Studies were 3T comprising T2, DWI, ADC and T1-weighted +/- fat saturation +/- IV gadolinium, +/- subtraction. DCE was read on the dynamics or DynaCAD (Invivo, Gainesville, FL, USA). Fellowship-trained breast radiologists blindly double-read by consensus; additional reader/s arbitrated. The reference standard was the histopathology result or cancer registry notification for cancer diagnoses and benign biopsies, benign follow-up imaging or subsequent screening MRI. RESULTS: Of 993 MRI studies in 554 women, 870 eligible MRI were performed in 471 women, and 706 had a reference standard. Median age was 44 years (range 18-80). The majority of studies (65% 457/706) were screening Medicare rebate-eligible high familial risk; 26% for surveillance after a breast cancer or contralateral staging; 6% screened BRCA carriers. Eleven cancers were diagnosed, eight were MRI-detected. Only two of these were at high-risk screening MRI. Five were detected at staging contralateral ILC, after negative 2D mammography and ultrasound. Cancer prevalence was highest for staging contralateral ILC, at 600/10,000 MRI, for high-risk screening 77/10,000 MRI and surveillance 116/10,000 MRI. CONCLUSIONS: Cancers were predominantly detected in women undergoing preoperative staging of new invasive lobular carcinoma in the contralateral breast, rather than the Medicare rebate-eligible high-risk screening group.