Joining FORCES is the FORCE newsletter with news, views and supportive information for individuals concerned about hereditary breast and ovarian cancer.
by Sue Friedman
Presenter: Timothy Rebbeck, PhD
Estimated cancer risks for BRCA1 and BRCA2 mutation carriers vary substantially between different research studies. Breast cancer risk estimates range from 30 to 85% by age 70, while lifetime ovarian cancer risk ranges from 40 to 60% among BRCA1 mutation carriers, and between 16 to 27% in women with BRCA2 mutations. In part, these variances are the result of specific populations studied (e.g., high-risk hereditary cancer families compared to population-based individuals) and factors that modify risk in mutation carriers. These estimates are based on statistics; they apply to entire populations and may not reflect an individual's cancer risk. This disparity adds to the confusion many BRCA mutation carriers feel when they attempt to make risk-management decisions. A more accurate estimate of personal risk would be helpful as a woman may approach a 30% lifetime risk of breast cancer differently than an 85% risk.
Factors called risk modifiers increase or decrease individual risk. Modifiers for breast cancer risk include exposures to certain environmental chemicals; hormones, pregnancy, and breastfeeding; diet and exercise; and other genes that may affect cancer risk in people with BRCA mutations.
Dr. Timothy Rebbeck and others are researching whether the type and position of specific mutations in BRCA1 or BRCA2 genes could explain some cancer risk variations. In previous studies, women with mutations around the exon 11 regions of both BRCA1 and BRCA2 genes appeared to have relatively higher risk for ovarian cancer and relatively lower risk for breast cancer. Researchers refer to this area as the "ovarian cancer cluster region" (OCCR), highlighting that specific mutations confer very different cancer risks. Despite this provocative finding, the mechanism of the OCCR effect is unknown, and the information has not yet translated into more precise risk assessment.
Recently, the worldwide Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA) has begun a systematic evaluation of BRCA1 and BRCA2 mutations. This effort aims to clarify risks associated with specific regions of genes or types of mutations, which may lead to more accurate risk assessment based on a mutation's location or whether a particular protein is abnormal or absent. Improved risk estimates may not eliminate the need for risk-reducing oophorectomy or strategies, but they may allow a tailored approach to the timing and type of these interventions.