Abstract P2-18-12: Surgical management of breast cancer: Breast conserving surgery or mastectomy in the 2010 SEER registries by hormone receptor and HER2 status
Authors: Schroeder MC , Sugg SL , Brooks JM , Thomas A 
Published: August 2014

Abstract
Background
Breast conserving therapy and mastectomy have been shown to have similar overall survival outcomes in large trials. After many years of decline, mastectomy rates are on the rise for a variety of reasons. In this context, there is increasing discussion that the risk of loco-regional recurrence is complex and varies by breast cancer subtype. Several, pre-trastuzumab-era, reports have shown that loco-regional recurrence is higher for HER2+ and triple negative breast cancer (TNBC) patients who undergo breast conserving therapy (BCS) compared with women with hormone receptor positive (HR+) disease. Other literature has suggested that some breast cancer subtypes have better outcomes with BCS. To provide the most recent data on surgical choice by breast cancer subtype, we report BCS and mastectomy rates from 2010 SEER data. Surgical choice is presented for ductal carcinoma in situ (DCIS) and invasive breast cancer. For women with invasive disease the subcategories of HR+, HER2+ and TNBC are reported.
Methods
SEER data were used to identify incident breast cancer patients diagnosed in 2010. Only pathologically confirmed cases were included. In addition, individuals were excluded if they were diagnosed at autopsy or by death certificate, did not receive surgery or if the type of surgery was unknown. Patients were categorized as having received BCS or mastectomy and, for invasive disease, by receptor subtype (HR+, HER2+ and TNBC). For invasive cancers, patients with unknown receptor subtypes were excluded.
Results
SEER data for 2010 included 65,598 women, 13,849 (21.1%) women had DCIS and 51,749 (78.9%) had invasive disease (Table 1). For invasive cancers after excluding 5,062 patients with unknown receptor status, 12.1% were TNBC, 14.4% were HER2+, and 83.5% were HR+. Overall, 43.5% of women underwent mastectomy (33.2% for DCIS). Mastectomy rate increased by stage at diagnosis: 33.5% for Stage I, 53.9% for Stage II disease and 77.8% for Stage III (OR = 0.49, p&lt;0.001 for Stage 1 compared to other stages). By age, mastectomy rates were 69.0% for &lt;30, 53.4% for 30-49, 43.3% for 50-59, 39.0% for 60-69, 39.4% for 70-79 and 41.1% for 80+ (OR = 2.90, p&lt;0.001 for women under 30 compared to older women).
Conclusions
In this large, recent series, 43.5% of women underwent mastectomy. This rate is among the highest reported from population-based registries and suggests a continued trend of increasing mastectomy rates. Women with HER2+ and TNBC were younger and significantly more likely to have mastectomy than their HR+ counterparts. Women with HER2+ breast cancer, in this trastuzumab-era cohort, were the subtype most likely to choose to undergo mastectomy. Monitoring for relapse events could contribute to a better understanding of how loco-regional recurrence risk might vary by subtype and surgical choice.
Table 1: Percent receiving BCS and mastectomy by subtype for invasive cancersReceptor StatusNMean AgeBCS (%)Mastectomy (%)Odds Ratio*p valueFull cohort51,74961.354.145.9 HR+38,98161.855.744.30.68&lt;0.001HER2+6,73858.143.056.01.61&lt;0.001TNBC5,65858.849.150.91.26&lt;0.001* Odds Ratio of undergoing mastectomy versus lumpectomy for this subtype compared to those not of this subtype.
Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-18-12.