The Value of Preoperative MRI in Breast Cancer Treatment

Abstract: Breast magnetic resonance imaging (MRI) remains controversial as an image adjunct in preoperative settings in terms of short-term benefits and there are no survival data from randomized studies. This prospective, randomized, multicentre study included 440 patients (age ≤ 56 y) with breast cancer from three large-volume Swedish breast clinics. Patients were randomized to either preoperative staging with breast MRI in addition to conventional assessment (n = 220) or to a no breast MRI group (n = 220). Treatments of all patients were discussed at multidisciplinary team conferences. Breast MRI provided additional information in 38% of the patients, and this caused a change in treatment plan for 18%. A change from suggested breast conservation to mastectomy occurred in 15%. The in-breast reoperation rate was statistically significantly lower in the MRI group: 5% vs 15% in the control group (P< 0.001). Although there was a higher MRI-related conversion rate from breast conservation to mastectomy, the final number of mastectomies did not differ between the two groups. The positive predictive value (PPV) of all incremental MRI findings was 74% (95% confidence interval, CI, 60–84%) in the group of patients with altered treatment plans and 27% (95% CI 14–44%) in the group of patients without such plans. In 20 of the 22 cases of conversions from breast-conserving surgery to mastectomy, the PPV for the decisive incremental MRI finding was 91% (95% CI 69–98%) and the PPV for the remaining decisive incremental findings was 83% (95% CI 68–92%). The empirical area under the curve for the MRI group based on receiver operating characteristic analysis was 0.85 (95% CI 0.78–0.91). In our retrospective study conducted in Vasteras County Hospital Breast Unit, preoperative MRI did not reduce the reoperation rates: 1.2% in 2018 vs 3.1% in 2016, when no-MRI was performed. Additional findings were observed in 10% of MRI examinations and more often in younger patients for whom mastectomy was suggested more often. MRI resulted in no delay of surgery. After 10 years of follow-up, the risk of relapse or death was 46% higher in the control group than in the MRI group and the risk of death was 27% higher, although the differences were not significant statistically. Locoregional, distant and contralateral recurrence outcomes combined were increased in the control group (P = 0.048). These results indicate that breast MRI significantly reduced the breast reoperation rate and important incremental findings in younger patients, without increasing the final number of mastectomies. These results could not be confirmed by our retrospective study in which MRI had no impact on the re-excision rate. Preoperative breast MRI provided incremental findings with a high degree of concordance with histopathology and resulted in slightly but non-significantly improved disease-free or overall survival rates after 10 years of follow-up.