Abstract P6-10-03: Bilateral Prophylactic Mastectomy in Swedish Women at High Risk of Breast Cancer — A National Survey

Background: Prophylactic mastectomy is the most efficient risk-reducing strategy for women with hereditary increased risk of breast cancer. Usually it is combined with immediate breast reconstruction. Unpublished data show that about 60% of Swedish female BRCA1/2 mutation carriers undergo bilateral prophylactic mastectomy (BPM) within eight years after mutation status disclosure. This study attempted a national inventory of all bilateral prophylactic mastectomies performed between 1995 and 2005 in high-risk women without a previous breast malignancy. The primary aim was to investigate the breast cancer incidence after surgery. Secondary aims were to describe the preoperative risk assessment, operation techniques, histopathological findings, complications, and regional differences. Methods: Geneticists, oncologists, and surgeons performing prophylactic breast surgery were asked to identify all women eligible for inclusion in their region. The medical records were reviewed in each region during 2006 and 2007 and the data were analyzed centrally. Information about cancer and death was recorded through 2008. The BOADICEA risk assessment model was used to calculate the number of expected/prevented breast cancers during the follow-up period. Women with incidental cancer in the breast specimens and women treated for ovarian cancer were excluded from the calculation. Prophylactic salpingo-oophorectomy performed before BPM was considered to have reduced the risk of breast cancer by 50%. Results: A total of 223 women operated on were identified. During a mean postoperative follow-up of 6.6 years (range 2.1-14.0), no primary breast cancer was observed. However, one woman succumbed nine years after BPM to widespread adenocarcinoma of uncertain origin. According to our risk calculation, based on 204 women and 1362 woman-years, approximately 12 breast cancers would have been expected, had BPM not been performed. Eight of these would have occurred in mutation carriers. The operations had been performed in eight hospitals throughout the country. One hospital performing BPMs declined participation in the study. Median age at BPM was 40 years. A total of 58% were BRCA1/2 mutation carriers. Five women (2%) had a lifetime risk of breast cancer Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-10-03.