Preoperative breast MRI reduces reoperations for unilateral invasive lobular carcinoma: a patient-matched analysis from the MIPA study.

Objectives: To investigate the surgical impact of preoperative breast MRI in patients diagnosed with invasive lobular breast cancer (ILC) in a prospective observational study.

Methods: The prospective MIPA observational study database was queried for patients aged 18-80 with newly diagnosed unilateral ILC at needle biopsy referred for primary surgery. Patients who underwent preoperative MRI (MRI group) were matched (1:1) with those who did not (noMRI group) according to nine confounding covariates. Surgical outcomes were compared between the matched groups with nonparametric statistics after calculating odds ratios (ORs).

Results: A total of 547 women with unilateral needle biopsy-diagnosed ILC were identified (158 noMRI group, 389 MRI group). After patient matching, each group retained 103 patients, for a total of 206 matched patients. For the rate of women having a first-line mastectomy, there was no significant difference between the MRI group (21.4%, 22/103; p = 0.727; OR 1.20, 95% CI: 0.61-2.38) and the noMRI group (18.4%, 19/103). Conversely, the reoperation rate in the MRI group (1.9%, 2/103) was significantly lower (p = 0.007; OR of avoiding reoperation 7.29, 95% CI: 1.60-33.21) than in the noMRI group (12.6%, 13/103 patients). Overall mastectomy rates (first plus second-line) did not significantly differ between the MRI group (23.3%, 24/103; p = 0.867, OR 1.12, 95% CI: 0.58-2.16) and the noMRI group (21.4%, 22/103).

Conclusions: Women who had preoperative MRI after a needle biopsy diagnosis of ILC had a significant six-fold reduction in reoperations compared to those who did not have an MRI examination, with similar overall mastectomy rates.

Key points: Question No randomized controlled trials investigating the impact of preoperative MRI on surgical outcomes (mastectomy rates and reoperation) of needle-biopsy-diagnosed ILC have been conducted. Findings In a patient-matched analysis of 103 vs 103 women, preoperative MRI led to a greater than six-fold reduction of reoperations, without significant differences in first-line and overall mastectomy rates. Clinical relevance In the absence of randomized controlled trials, patient matching can be applied to mitigate confounding factors that drive the referral to preoperative MRI, showing that preoperative MRI has beneficial effects on surgical outcomes in patients with needle biopsy-diagnosed unilateral ILC.