Abstract P4-02-01: Only in lobular breast cancer MRI use is associated with a lower risk of positive surgical margins and a reduced number of mastectomies. A real-world analysis in The Netherlands
Authors: Tjan-Heijnen VC , Lobbes MB , Vriens IJ , van Bommel AC , Nieuwenhuijzen GA , Smidt ML , Boersma LJ , van Dalen T , Smorenburg CH , Siesling S , Voogd AC 
Published: May 2016

Abstract
Background
The value of magnetic resonance imaging (MRI) for patients with breast cancer remains under debate. Breast MRI may contribute to the planning of local therapy, but also bears the risk of overtreatment. We analyzed the use of MRI and its impact on surgical treatment and risk of detecting contralateral breast cancer in the Netherlands.
Patients and methods
All patients who underwent primary surgery for stage I-III invasive breast cancer in the years 2011-2013 were identified through the Netherlands Cancer Registry. The following data were documented: year of diagnosis, hospital type and volume, age at diagnosis, clinical T and N stage, histological type and grade, presence of multifocality in resection specimen, hormone receptor status, HER2 status and use of MRI. We analyzed whether MRI use was related to type of surgery (primary or secondary mastectomy or breast conserving surgery), surgical margin involvement, and diagnosis of synchronous contralateral breast cancer.
Results
MRI was performed in 10,819 (29,8%) out of 36,333 patients newly diagnosed with invasive breast cancer and treated with primary surgery in the years 2011-2013 in the Netherlands. Use of MRI did not clearly increase in this period.
In the multivariate analysis, patients younger than 50 years of age compared to patients aged 70 years or older (OR 6.34, 95% CI 5.86-6.87), patients with lobular breast cancer compared to those with ductal carcinoma (OR 3.46; 95% CI 3.23-3.70) and patients with multifocal tumors compared to those without multifocality (OR 2.30, 95% CI 2.15-2.45) were more likely to undergo MRI. Hospital volume (&lt;150 versus &gt;150) was only marginally related to MRI use (OR 0.93; 95% CI 0.87-0.99).
Patients with invasive breast cancer undergoing MRI were more likely to undergo primary mastectomy than those without MRI (OR 1.21; 95% CI 1.15-1.28), but the subgroup with invasive lobular cancer undergoing MRI were less likely to undergo primary mastectomy (OR 0.85; 95% CI 0.75-0.98). A significantly lower risk of positive surgical margins was seen in patients with lobular breast cancer and breast conserving surgery who had undergone MRI as compared to those without MRI (OR 0.58, 95% CI 0.44-0.78) and, consequently, also a lower risk of secondary mastectomy (OR 0.60, 95% CI 0.41-0.87). Risk of positive surgical margins was not reduced by MRI use in patients with invasive ductal carcinoma (OR 0.91; 95% CI 0.77-1.07). Patients who underwent MRI were almost four times more frequently diagnosed with contralateral breast cancer, compared to those in whom MRI was not performed (OR 3.60, 95% CI 3.06-4.24).
Conclusion
Breast MRI was significantly more often used in younger patients, patients with lobular and/or multifocal breast cancer. Interestingly, MRI use was associated with less primary and secundary mastectomies in lobular invasive breast cancer, in contrast to an increased number of primary mastectomies in patients with invasive ductal cancer. MRI was further associated with an almost fourfold higher incidence of contralateral breast cancer.
Citation Format: Tjan-Heijnen VC, Lobbes MB, Vriens IJ, van Bommel AC, Nieuwenhuijzen GA, Smidt ML, Boersma LJ, van Dalen T, Smorenburg CH, Siesling S, Voogd AC. Only in lobular breast cancer MRI use is associated with a lower risk of positive surgical margins and a reduced number of mastectomies. A real-world analysis in The Netherlands. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-02-01.