Oncologists have known certain chemotherapies and specific types of radiation therapy can trigger secondary cancers later in life, which is why childhood cancer survivors are encouraged to have earlier screening tests than the general population. Among women treated with chest radiation as children, up to 20 percent of them will develop breast cancer by age 45. These women, therefore, should receive annual screening mammograms starting at age 25 or eight years after radiation treatment, whichever comes first.
However, a study published in late January in the Journal of the American Medical Association found that many female survivors who received chest radiation are foregoing breast cancer screening. The study included women who participated in the large Childhood Cancer Survivor Study, which has produced much of the information known about late and long-term effects in this population. The study questioned women who received chest radiation for childhood cancer about their screening habits, along with childhood cancer survivors who did not receive chest radiation. In women under 40, researchers found that only 23.3 percent of survivors who received chest radiation had a screening or diagnostic mammogram within the past year, while 47.3 percent never had a mammogram.
A possible explanation for the low screening rates is lack of physician referral. Survivors under 40 with a history of chest radiation who reported a physician recommending a screening mammograms were much more likely to get one than those under 40 who did not (76 percent versus 17.6 percent). The two most common reasons given by women under 40 for not receiving a screening mammogram within the past two years were the “doctor didn’t order it” (31 percent) and “I’m too young” (30 percent).
Another issue oncologists have run up against is mammography may be less effective in the under 40 group, primarily because younger women have denser breasts than older women, making it more difficult to use mammography to find breast tumors. For that reason, several groups, including the American Cancer Society, also recommend breast magnetic resonance imaging (MRI) in addition for women at high risk of breast cancer, including those who have a BRCA gene mutation or prior chest radiation. An accompanying editorial to the JAMA article raised the issue of whether MRI should be used as a replacement to mammography since MRI doesn’t carry the small, but present, dose of radiation that comes with mammography.
Although chest radiation is not used as often to treat childhood cancers because of the high risk of secondary cancers, there are still up to 25,000 female cancer survivors over age 25 who are at risk because of their history of chest radiation.
Read more about secondary cancers in “Battling Cancer Again,” in CURE’s Spring 2009 issue.