Surveillance for Breast Cancer After Childhood Cancer

Abstract

BREAST CANCER IS A RECOGNIZED COMPLICATION OF chest irradiation for childhood cancer, and surveillance for breast cancer with regular clinical examination and annual screening mammography starting at age 25 years or 8 years after radiation is recommended. However, uptake of screening mammograms in this high-risk group is suboptimal, as shown in the report by Oeffinger and colleagues in this issue of JAMA. The authors examined breast cancer surveillance practices in a survey of 625 female survivors of pediatric cancer who were between 25 and 50 years and participants in the longitudinal Childhood Cancer Survivor Study (CCSS). These survivors were at a significantly increased risk of breast cancer as a result of treatment they received in the form of moderateto high-dose ( 20 Gy) irradiation to the chest for treatment of a childhood cancer (chest RT group). The women in the chest RT group were compared with 639 similarly aged CCSS participants who did not receive chest irradiation and with 712 siblings in the CCSS siblings cohort. Oeffinger et al found that 55% of the women in the chest RT group reported having a screening mammogram within the previous 2 years. Rates of screening mammography varied by age at the time of the survey, with 23.3% of women aged 25 through 39 years and 53.6% of women aged 40 through 50 years reporting a screening mammogram in the previous year. Among women in the younger group, those who reported a physician recommendation for screening were 3 times as likely to have had screening in the previous 2 years when compared with those whose physician did not recommend that they have a mammogram. In light of a recognized increased risk of breast cancer following radiation to the chest, chest irradiation is now used less frequently for the curative treatment of some pediatric cancers, which include different types of childhood cancer including Hodgkin disease, Wilms tumor, neuroblastoma, and non-Hodgkin lymphoma; however, there are an estimated 20 000 to 25 000 adult survivors of pediatric cancer older than 25 years in the United States who are in this risk category. Current Childhood Oncology Group (COG) guidelines for breast cancer surveillance after pediatric cancer in the United States recommend yearly clinical breast examination from the age of puberty until age 25 years, and then every 6 months if the survivor was treated with irradiation of at least20 Gy to mantle, minimantle, mediastinal, chest (thoracic), or axillary fields. In addition, it is recommended that these survivors have annual mammography and an adjunct breast magnetic resonance imaging (MRI) starting at age 25 years or 8 years after radiation, whichever is last. The effectiveness of the standard mammogram in detecting preinvasive and invasive breast cancer is known to be relatively poor in young women due to the density of breast tissue in this age group, increasing the importance of MRI in the detection and diagnosis of breast cancer in younger women with dense breast tissue. The estimated dose of radiation from a standard 2-view screening mammogram is approximately 3.85 mGy per mammogram. Although it is accepted that the additional dose is small compared with the higher therapeutic dose already received, it is not known to what extent repeated exposure to small doses of breast irradiation in women already at an increased risk of breast cancer may result in a significantly increased risk of second primary breast cancer. This is an important question that needs to be addressed in future studies. The generally low uptake rate of screening mammogram in a high-risk population of pediatric cancer survivors has also been highlighted in a previous study of adult survivors. Some factors associated with the uptake of breast screening including age and race/ethnicity, physician recommendation, health beliefs, and personal understanding of breast cancer risk were explored by Oeffinger et al, but economic factors were not. Thus, whether the cost of annual breast cancer screening was a factor in this cohort is not known. In comparison, among a population of 461 Australian women at an increased risk of developing hereditary breast cancer, uptake of breast screening was 89% overall, although it decreased to 77% among those