Breast magnetic resonance imaging use in patients undergoing neoadjuvant chemotherapy is associated with less mastectomies in large ductal cancers but not in lobular cancers

Background To assess the impact of breast magnetic resonance imaging (MRI) use on surgical outcome per histological breast cancer subtype in patients treated with neoadjuvant chemotherapy. Patients and methods All patients aged 18–70 years who underwent neoadjuvant chemotherapy for stage I–III invasive breast cancer in the Netherlands in the years 2011–2013 were identified from the Netherlands Cancer Registry. Patients with cT4 tumours were excluded from the analysis. Use of breast MRI and impact on surgical treatment, resection margins and detection of contralateral breast cancer were analysed by multivariable analyses. Results Breast MRI was performed in 2879 (83.9%) out of 3433 patients treated with neoadjuvant chemotherapy. Younger age (odds ratio [OR] 1.42; 95% confidence interval [CI] 1.17–1.71 for 18–50 years compared with 50–70 years), larger tumour stage (OR 1.46 [95% CI 1.15–1.86] for cT3, compared to cT1–2 tumours) and multifocality (OR 1.30; 95% CI 1.04–1.61, versus unifocality) were associated with increased breast MRI use. In ductal breast cancer, after stratification for cT-status, breast MRI use is associated with a significant lower OR for mastectomy as final surgery in cT3 tumours (OR 0.45, 95% CI 0.21–0.99). Resection margin involvement and detection of contralateral breast cancer were not associated with breast MRI use. Conclusion In patients treated with neoadjuvant chemotherapy, the use of breast MRI was associated with a reduced mastectomy rate, particularly in patients with large invasive ductal breast tumours but not in patients with lobular breast cancer