Background: Breast cancer is the second most common cancer in women and the second leading cause of cancer death in the US. Women with a diagnosis of breast cancer have a risk of developing contralateral breast cancer of up to 11%. Despite lack of clear evidence supporting an increase in the rate of the procedure, rates of contralateral prophylactic mastectomy (CPM) increased dramatically in the past 10 years. Genetic predisposition to breast cancer is an indication for CPM, however it is inconsistently documented. We sought to explore the trends in CPM and variables associated with CPM and genetic counseling within a large healthcare system over a 15-year period.

Methods: Retrospective review of CPM documented by the Network Tumor Registry period 1994 — 2008 performed within a four hospital health system in Louisville, KY. We calculated time trends of CPM as a proportion of mastectomy patients each year, and we analyzed clinical, pathologic, and demographic variables among mastectomy patients who underwent CPM compared to those who did not have procedure. Descriptive variables included: age, year of diagnosis, tumor grade, tumor stage, tumor size, tumor histology type, estrogen receptor status, progesterone receptor status, lymph node status, node dissection type previous cancer diagnosis, family history, menopausal status, use of immediate reconstruction, and type of insurance. Our statistical analysis included chi-square (x2), and odds ratios (OR) to determine differences among groups. We evaluated the prevalence and timing of genetic testing among CPM patients by matching CPM patient level data with a prospectively maintained genetic testing comprehensive database. CPM patient level data was matched with corresponding genetic counseling data to determine the trends in usage of genetic counseling.

Results: During the study period, 2,496 women with stage I-III invasive breast cancer underwent mastectomy: 2,288 (91.7%) had unilateral mastectomy (UM) alone and 208 (8.7%) underwent UM and CPM. The proportion of all female mastectomy patients who had CPM increased from 0% in 1994 to 27.1% in 2008. Variables significantly associated with CPM were: Age under 65, immediate breast reconstruction, private insurance, family history of cancer and lobular tumor histology. Favorable tumor characteristics such as stage I and tumor size of < 1cm were associated with higher CPM rates, compared to > Stage I disease and tumors > 1cm. There was a statistically significant association with CPM and negative lymph nodes and a history of hormone use. No differences were found in UM vs. UM+CPM by race, ethnicity, tumor grade, ER/PR status or previous history of cancer. Among the 208 CPM patients, 44 (21.2%) received genetic testing and 6 (2.9%) were positive for BRCA mutations. Of the 44 women who received genetic testing, 5 (11.4%) did so prior to surgery.

Conclusions: Performance of CPM was associated factors such as small tumor size and age <65 and private insurance. Genetic counseling was rarely used in the risk-assessment of potential CPM patients. Given the increasing frequency of this procedure, this warrants further investigation.

Citation Information: Cancer Prev Res 2010;3(12 Suppl):B6.