Preoperative MRI and Its Impact on Surgical Outcomes in Patients with Triple Negative Breast Cancer Treated with Primary Surgery: Did New Margin Guidelines or Cavity Shave Margins Practice Diminish the Role of Preoperative MRI?

BACKGROUND: Results of an earlier retrospective study from our institution suggested that patients with triple negative breast cancer (TNBC) who had preoperative MRI may have had an improved local recurrence rate (LRR) after breast conserving surgery (BCS). We aimed to clarify the impact of preoperative MRI on surgical outcomes in an expanded TNBC cohort treated by BCS in a contemporary era. METHODS: Our study cohort comprised 648 patients with TNBC who underwent BCS between 2009 and 2018. Demographic and clinical characteristics were compared between those with (n = 292, 45.1%) and without (n = 356, 54.9%) preoperative MRI. Multivariable logistic regression was performed to assess the association of preoperative MRI with surgical outcomes. RESULTS: The crude LRR of 3.5% was lower than previously reported. Univariable analyses demonstrated that the LRR and re-excision rates in the MRI and no-MRI groups were 3.4 and 3.7%, 21.6% and 27.2%, p = 0.876 and p = 0.10, respectively. Multivariable logistic regression analyses demonstrated that preoperative MRI was not associated with a lower LRR: odds ratio (OR) = 1.42 (p = 0.5). During our study period, new margin guidelines and shave margins practice were adopted in 2014 and 2015. To account for their effects, the year of diagnosis/surgery and other clinical variables were adjusted in multivariable logistic regression and inverse probability weighting models to demonstrate that preoperative MRI remained associated with a lower re-excision risk, OR 0.56, p = 0.04l; and a lower re-excision rate, 23.15% versus 36.0%, p < 0.01, respectively. CONCLUSIONS: Our findings suggested that patients with TNBC anticipating BCS may benefit from preoperative MRI.