Operative Approach and PREOPERATIVE BREAST MRI USE FOR PATIENTS WITH SYMPTOMATIC INVASIVE LOBULAR CANCER GEORGE Ikpokomitop1, MCCARTAN Damian1, DUKE Dierdre2, HAMBLY Niamh2, KERR Jennifer2, ALLEN Michael1, POWER Colm1, HILL Arnold1 Departments of 1. Surgery and 2. Radiology, Beaumont Hospital, Dublin 9 Background Aim Methods In patients with infiltrating lobular breast cancer (ILC) the use of MRI for local staging is attractive due to the reduced sensitivity of mammography and ultrasonography with this histological subtype. Historical series have also highlighted a higher risk of multicentric and bilateral disease in patients with a newly diagnosed ILC. However, MRI does not reduce the margin positivity rate in patients treated with breast conserving surgery (BCS). A meta-analysis of four studies and 3169 patients also found that there was no difference in the rate of local recurrence at eight years for patients receiving a preoperative breast MRI compared with those without preoperative imaging 1,2. The aim of this study was to investigate the use of MRI in patients who present through a symptomatic breast clinic and a newly diagnosed ILC. A retrospective database was established of patients with a newly diagnosed ILC at our symptomatic breast clinic between over a 6-year period from January 2009 and December 2014. Anonymised data was extracted from hospital pathology, radiology as well as details of operative intervention. Eligible patients were those with a newly diagnosed, stage I-III ILC. Patients with a mixed IDC/ILC were excluded. Statistical analyses were carried out using MINITAB soft-ware. A p-value <0.05 was considered significant. Fisher’s exact test was used for comparison of categorical data. The Mann–Whitney U-test was used for continuous variables. Figure 1: Sagittal breast MRI post gadolinium Results Operative Approach and Tumour Size Demographics Breast Operation A total of 94 women with a mean age of 62 were diagnosed with ILC and underwent surgery during the 6-year study period. MRI (n=63) No MRI (n=31) p-value Successful BCS 16% 35% 0.039 Margin Re-excision 60% 9% 0.024 BCS to completion mastectomy 10% 1.000 Straight to mastectomy 73% 55% 0.063 The most common operative approach for patients presenting with a symptomatic ILC was to proceed straight to mastectomy. In keeping with guideline recommendations, the majority of patients with pT3 or pT4 tumours proceeded directly to mastectomy. A small proportion of patients with a tumour less than 20mm in the MRI group were treated with a mastectomy. MRI No MRI % of patients Table 1: Surgical approach in patients who did and not receive pre-operative breast MRI MRI (n=47) No MRI (n=17) p-value pT1 9% 0% 0.566 pT2 32% 29% 1.000 pT3/4 60% 71% 0.562 Overall, two thirds of patients proceeded directly to a mastectomy as the primary operative intervention for their ILC. The use of pre-operative MRI did not appear to influence this choice. A further 10% of patients proceeded to mastectomy after an attempt at BCS and similarly this rate did not differ between those who did and did not have a pre-operative MRI. The proportion of patients who successfully completed BCS was higher in the group who did not have an MRI with the rate of margin re-excision higher in the MRI group. Figure 2: Of the 94 women with a newly diagnosed, stage I-III ILC, 67% underwent a pre-operative breast MRI. Overall 45% had a pT3 or T4 cancer. There did not appear to be a pattern to the selection of patients for an MRI based on primary tumor size. A contralateral breast cancer was identified in 6 of the 64 patients who received an MRI. Patients who received an MRI were considerably younger (median 53 vs 75 years, p<0.001). Table 2: Patients proceeding straight to mastectomy based on pT stage In patients with pT1 or pT2 cancers the direct to mastectomy rate in those who had an MRI was 70% for patients aged under 70 compared to 17% for those older than 70 (p=0.029). Conclusion Our data is limited in that it does not take into account other factors such as tumour location and breast size that influence the decision to undergo a mastectomy. However, in younger patients with a T1-2 ILC that is potentially amendable to BCS the mastectomy rate, at 70%, remains high. Breast MRI is a highly sensitive imaging modality and while access is improving it remains a costly investigation and one that is not always readily accessible. Our results demonstrate that a high proportion of patients with ILC presenting through a symptomatic clinic will be primarily treated with a mastectomy regardless of MRI. References An individual person data meta-analysis of preoperative magnetic resonance imaging and breast cancer recurrence. Houssami N et al. J Clin Oncol. 2014;32(5):392-401. Comparative effectiveness of MRI in breast cancer (COMICE) trial: a randomised controlled trial. Turnbull L et al. Lancet. 2010;375(9714):563-71