A 65% reduction in all-cause mortality was associated with oophorectomy.
Women who carry either the BRCA1 or BRCA2 gene have a 70% likelihood of developing breast cancer during their lifetime, as well as high risks of second primary breast and ovarian cancers if they do develop breast cancer.
Researchers from the Women's College Research Institute in Toronto, Canada, set out to confirm these previous observations, studying a group of 676 women with BRCA1 or BRCA2 gene mutations and early-stage breast cancer.
Among the study participants, 345 underwent oophorectomy - a procedure to remove the ovaries - while the remaining 331 women retained both ovaries.
Overall, 77.4% of all participants were still alive after 20 years. The researchers found a 56% reduction in breast cancer death to be associated with oophorectomy, with this reduction rising to 62% among women carrying the BRCA1 mutation.
However, women carrying the BRCA2 mutation who underwent oophorectomy had only a 43% reduction in breast cancer death, which the researchers say was not statistically significant. A 65% reduction in deaths from all causes was found to be associated with oophorectomy.
In the study, oophorectomies were performed 6 years on average after the women received a diagnosis of breast cancer.
Seventy of the participants who carried BRCA1 had their ovaries removed within 2 years of their diagnosis, and the authors observed a 73% reduction in death among this group. The researchers found that the protective effect of the procedure was immediate and lasted for 15 years.
Results validate oophorectomy as boosting survival rates for BRCA1 carriers
"The results provide a validation of the role of oophorectomy in conveying both a disease-free and overall survival benefit for BRCA1 mutation carriers," writes Dr. Mary L. Disis, editor-in-chief of JAMA Oncology, who published the study. She continues:
"In the entire group, oophorectomy was particularly effective for survival benefit in women with estrogen receptor-negative breast cancer. The data reported here are compelling and suggest that the potential of oophorectomy should become part of the treatment discussion at the time of diagnosis for BRCA mutation carriers with early-stage breast cancers."
The study authors say that one limitation to their research is that the study only looked at women with stage 1 and stage 2 breast cancer, so the results may not apply to women with advanced-stage breast cancer.
Also, because the women in the study were treated prior to the introduction of aromatase inhibitors - drugs that work by blocking the aromatase enzyme, which turns the androgen hormone into cancer-stimulating estrogen - the study could not evaluate how recent antihormonal drugs might have influenced the findings.
The researchers say that the strengths of their study include the large sample size and the confirmation of all treatments by review of medical records. Deaths from breast cancer were also distinguished from deaths from other causes.
Another strength was that both untested and deceased women were included in the study to avoid the survivorship bias that the authors say would arise if genetic testing was a condition for inclusion - although 90% of the participants were confirmed mutation carriers.