Maurie Markman, MD
The increased risk of developing breast and ovarian cancer associated with mutations in the BRCA1/2
genes has generated a host of recommendations on early detection and prophylactic strategies for those deemed at higher risk. Optimal testing strategies, including when to start testing and which prophylactic approach to pursue, have remained a topic of debate.
A controversial paper published by the discoverer of the BRCA
gene, Mary-Claire King,PhD, recently suggested that current screening strategies were inadequate (JAMA
. 2014;312:1091- 1092). The paper detailed that BRCA
mutations are not commonly identified until after a cancer diagnosis, which King labeled as a failure of cancer prevention. To address the problem, King, from the University of Washington, recommended that all women should be tested for BRCA
mutations starting at age 30.
A panel of experts discussed these recommendations during an OncLive
Peer Exchange® discussion that was moderated by Maurie Markman, MD, from Cancer Treatment Centers of America. The discussion included insights from Michael J. Birrer, MD, PhD, Robert A. Burger, MD, Warner K. Huh, MD, and James Tate Thigpen, MD.
Michael J. Birrer, MD, PhD
During the discussion, panelists agreed upon the importance of genetic screening, but disagreed with some of King’s finer points. Birrer, from the Massachusetts General Hospital, felt strongly that germline testing should be conducted for women diagnosed with ovarian cancer, but that testing for the general population was a different issue.
“[King’s paper is] looking at the general population with a broad screening approach in sequencing both BRCA1
,” Birrer said. “One needs to recognize that ovarian cancer is still a rare tumor. This is going to be extremely costly and I think not particularly cost-effective. I would not support this in the general population at this time.”
Rather than screening the entire population, panelists felt that testing should be limited to those at high-risk of having an alteration. Universal testing could be considered in certain high-risk groups, such as in the Ashkenazi Jewish population, noted Burger, from the University of Pennsylvania.
The primary evidence for the theory of population-based screening came from a study conducted in Israel, according to King. In this study, over 8000 Ashkenazi Jewish men were enrolled and screened for three loss-of-function mutations that cumulatively account for the majority of inherited cancer risk due to BRCA
in this population. In total, 175 men were identified as carriers of BRCA
mutations, with genetic testing offered to all female relatives.
Robert A. Burger, MD
Women identified in this way, and found to carry a BRCA
mutation themselves, had high cancer risks. Among carriers of BRCA1
, the risk of developing breast or ovarian cancer was 60% (margin of error 7%) by age 60 years and 83% (margin of error 7%) by age 80 years. Among carriers of BRCA2
, risk was 33% (margin of error 9%) by age 60 and 76% (margin of error 13%) by age 80 years.
These risks were higher at every age, among women born more recently versus those born earlier, King wrote. This trend has been observed in other studies and, according to the paper, “likely reflects increasing prevalence of nongenetic risk factors for breast cancer, including earlier age of menarche and later ages of childbearing, factors related to improved nutrition and education for women in modern society.”
In the study, 50% of families found to harbor a BRCA
mutation had no history of breast or ovarian cancer to garner clinical attention. Female BRCA
carriers from these lower-cancer-risk families had similar risks compared with their counterparts from higher-cancer-risk families. This, King writes, highlights the need for population-based screening.
The Peer Exchange panel did not dismiss the utility of genetic screening, but rather questioned the feasibility to be implemented in the general population.