Efficacy of prophylactic mastectomy in women with unilateral breast cancer: a cancer research network project.
OBJECTIVE
We investigated the efficacy of contralateral prophylactic mastectomy (CPM) in reducing contralateral breast cancer incidence and breast cancer mortality among women who have already been diagnosed with breast cancer.


METHODS
This retrospective cohort study comprised approximately 50,000 women who were diagnosed with unilateral breast cancer during 1979 to 1999. Using computerized data confirmed by chart review, we identified 1,072 women (1.9%) who had CPM. We obtained covariate information for these women and for a sample of 317 women who did not undergo CPM.


RESULTS
The median time from initial breast cancer diagnosis to the end of follow-up was 5.7 years. Contralateral breast cancer developed in 0.5% of women with CPM, metastatic disease developed in 10.5%, and subsequent breast cancer developed in 12.4%; 8.1% died from breast cancer. Contralateral breast cancer developed in 2.7% of women without CPM, and 11.7% died of breast cancer. After adjustment for initial breast cancer characteristics, treatment, and breast cancer risk factors, the hazard ratio (HR) for the occurrence of contralateral breast cancer after CPM was 0.03 (95% CI, 0.006 to 0.13). After adjustment for breast cancer characteristics and treatment, the HRs for the relationship of CPM with death from breast cancer, with death from other causes, and with all-cause mortality were 0.57 (95% CI, 0.45 to 0.72), 0.78 (95% CI, 0.57 to 1.06), and 0.60 (95% CI, 0.50 to 0.72), respectively.


CONCLUSIONS
CPM seems to protect against the development of contralateral breast cancer, and although women who underwent CPM had relatively low all-cause mortality, CPM also was associated with decreased breast cancer mortality.
Herrinton
Lisa J
LJ
Cancer Research Network, Division of Research, Northern California Kaiser Permanente, 2000 Broadway Ave, Oakland, CA 94612, USA. lisa.herrinton@kp.org
Barlow
William E
WE
Yu
Onchee
O
Geiger
Ann M
AM
Elmore
Joann G
JG
Barton
Mary B
MB
Harris
Emily L
EL
Rolnick
Sharon
S
Pardee
Roy
R
Husson
Gail
G
Macedo
Ana
A
Fletcher
Suzanne W
SW
D001943:Breast Neoplasms / Q000453:epidemiology / Q000401:mortality / Q000517:prevention & control* / Q000601:surgery; D015331:Cohort Studies; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D008408:Mastectomy; D015412:Mastectomy, Segmental; D009362:Neoplasm Metastasis; D016609:Neoplasms, Second Primary / Q000517:prevention & control*; D018579:Patient Selection; D012189:Retrospective Studies; D013997:Time Factors