Risks of mammography in BRCA positive women
This was submitted as a Letter to the Editor of the Montreal Gazette, on 2013-5-25:
re: “Angelina Jolie got it right” (Friday, May 24):
Dr. Labos is to be commended for his clearly written article on mastectomy for BRCA positive women. However, he did not mention that these unfortunate women are at higher risk for developing breast cancer from mammography itself. As he summarizes, the BRCA genes code for proteins which are important components of cellular mechanisms that repair chromosomal damage. Mutations to these genes thus cripple the repair mechanisms, allowing chromosomal damage to wreak havoc, including turning the cell cancerous.
One of the causes of chromosomal damage is ionizing radiation. X-rays, including mammograms, are a form of ionizing radiation, and can thus cause the damage that can lead to cancer. For BRCA positive women whose cells may not be able to repair this damage, the risk of developing breast cancer from mammography is elevated compared to women without BRCA mutations (a “supramultiplicative” interaction). What’s worse, the low energy radiation used in mammograms has a greater effect on tissue than that of many other medical X-rays. To add insult to injury, BRCA positive women are frequently advised to start having mammograms at an earlier age and more frequently, up to twice yearly as Dr. Labos points out. Cancer risk from radiation is cumulative with exposure, and younger women are thought to be at higher risk.
Angelina Jolie’s decision to undergo prophylactic double mastectomy will reduce her risk of developing breast cancer, not only by removing breast tissue, but also by ending the mammographies to which women with impaired DNA repair mechanisms caused by BRCA mutations are especially vulnerable.
Is prophylactic mastectomy the best choice for BRCA positive women? This question may become easier to answer when there are readily available, safer, and sufficiently accurate alternatives to mammography for breast cancer screening in this population.