More Moderate Risk Patients Pick Contralateral Prophylactic Mastectomy

San Antonio, TX—The increase in contralateral prophylactic mastectomy (CPM) appears to be driven by how the index breast cancer was managed, said Tari A. King, MD, Jeanne A. Petrek Junior faculty chair and principal investigator of the William F. Keck Laboratory for Breast Cancer Research at Memorial Sloan-Kettering Cancer Center (MSKCC), New York City. Dr King reviewed data for patients with unilateral breast cancer who underwent mastectomy. Many of the patients who chose CPM were not at increased risk for contralateral breast cancer and may have made their decision based on the amount of testing they underwent and a failed attempt at breast conservation surgery, she said at the CTRC-AACR San Antonio Breast Cancer Symposium.

To determine what may have influenced the increasing rate of CPM, Dr King abstracted data from the medical records of 2965 patients who underwent mastectomy for unilateral stage 0 to III breast cancer at MSKCC, representing 24% of all patients having definitive breast cancer treatment there from 1997 to 2005. Some 407 (13.7%) underwent CPM within 12 months of diagnosis. The rate of CPM increased from 7% in 1997 to 24% in 2005.

Patients who chose CPM were younger, more likely to be white, and more likely to have a family history of breast cancer compared to patients not choosing to have CPM (P <.0001 for all comparisons). “However, the family history profiles in this series do not support increased recognition of mutation carriers and truly high risk family history as major factors [in the choice of CPM],” said Dr King. “Most patients undergoing CPM were not at significantly increased risk for contralateral breast cancer.”

Among the patients who chose CPM, only 8% had two or more first-degree relatives with breast cancer. Compared to patients not choosing CPM, those who chose CPM more often had genetic testing performed (10% vs 29%; P <.0001) and were more often found to be BRCA mutation carriers (12% vs 31%; P <.0001).

Only 52 (13%) of the 407 patients who chose CPM were considered high risk (37 who were BRCA mutation carriers and 15 who had prior mantle radiation), she noted. Of the patients who opted for CPM, 22% had ductal carcinoma in situ only.

During the course of the study, the use of magnetic resonance imaging (MRI) at diagnosis increased from 1.3% to 36.3%, to parallel the increased rate of CPM. Among those undergoing CPM, 43% had MRI at cancer diagnosis, compared with only 16% of those not choosing CPM (P <.0001), she said. Twenty-nine percent of the patients who chose CPM had a contralateral/bilateral biopsy performed due to findings on the MRI, compared with only 4% of those not opting for CPM (P <.0001).

More than one-fourth (28%) of the women who chose CPM had breast conserving surgery attempted, compared with 16% of those not choosing CPM (P <.0001). Breast reconstruction was performed in 87% of the group undergoing CPM and 51% not undergoing CPM (P <.0001). The rate of CPM varied by surgeon, from 3% to 26%.

There was no association between CPM and estrogen receptor status of the tumor, nor with tumor size, further supporting the notion that patients may be choosing CPM for reasons other than future risk, said Dr King. Efforts to optimize breast conservation therapy and minimize unnecessary testing may help to curb the trend toward more use of CPM, she said.