January 29, 2009 — Despite guideline recommendations, the majority of young women at high risk for breast cancer because of chest-radiation treatment for childhood cancer are not being appropriately screened. A report published in the January 28 issue of JAMA found that 63.5% of women between the ages of 25 and 39 years and 23.5% of those between 40 and 50 years had not undergone mammography screening in the previous 2-year period.
"Women who have been treated for a pediatric cancer with moderate- to high-dose chest radiation have an increased risk of breast cancer at a young age," said lead author Kevin C. Oeffinger, MD, director of the Program for Adult Survivors of Pediatric Cancer at Memorial Sloan-Kettering Cancer Center, in New York CIty. "It is recommended that these women initiate breast cancer surveillance at a young age. The Children's Oncology Group and other international groups recommend an annual mammogram and breast magnetic resonance imaging (MRI) starting at age 25 years or 8 years after the radiation — whichever occurs last."
Most of the women in this risk group are not being followed-up at a cancer center, and both patients and clinicians might be unaware of this risk or of the current screening recommendations, Dr. Oeffinger told Medscape Oncology. "I think that the primary factor is that clinicians are not aware of this risk and so are not discussing breast cancer screening with these young women."
The median age of breast cancer diagnosis in this population ranges from 32 to 35 years, and the risk for disease begins to increase as soon as 8 years after radiation therapy. Breast cancer risk is greatest among women who received high-dose mantle radiation for Hodgkin's lymphoma, the authors note. It is estimated that from 12% to 20% of women treated with moderate- to high-dose chest radiation will be diagnosed with breast cancer by the age of 45 years. In addition, previous chest radiation and possible exposure to chemotherapy with anthracyclines often limits treatment options for the women who do subsequently develop breast cancer.
To date, published information about breast cancer surveillance practices in this population is limited. The goal of the current study was to determine the prevalence of screening mammography and to identify predictors of mammography and other methods of breast cancer surveillance in young female adult cancer survivors who were treated with radiation during childhood. The study cohort consisted of 551 women 25 to 50 years who had survived pediatric cancer, who had been treated with chest radiation, and who were participants in the Childhood Cancer Survivor Study (CCSS). Breast cancer surveillance was compared in the CCSS survivors, in similarly aged pediatric cancer survivors who had not been treated with radiation (n = 561), and in the siblings of CCSS survivors (n = 622).
Screening data were obtained with a 114-item cross-sectional survey that was administered by both mail and telephone interview between June 6, 2005 and August 24, 2006 to all study participants.
Lower Than Expected Screening Rates
Only 36.5% of women between 25 and 39 years with a history of chest radiation reported undergoing mammography screening in the previous 2 years. The rate was lower than the researchers had expected, but higher than in the other 2 groups. However, in the high-risk (chest radiation) group, nearly half (47.3%) had never had a mammogram, and only 23.3% had undergone screening or diagnostic mammography in the previous year.
Cancer survivors with chest radiation aged 40 to 50 years were more likely to report breast cancer screening than younger women. In the older group, 76.5% reported undergoing a screening mammogram in the previous 2 years; this rate was higher than in the 2 comparison groups (70.0% for cancer survivors without chest radiation and 67.0% for the CCSS sibling group). Of importance, the researchers noted, only about half (52.6%) of the women in the high-risk group had undergone regular screening, defined as at least 2 mammograms in 4 years.
Physician Recommendation the Strongest Predictor
For women 25 to 39 years old, the strongest predictor of mammography was having a physician recommendation, and the likelihood of undergoing a mammogram was 3 times higher among those who reported a physician recommendation than among those who did not.
Age was another important predictor of screening mammography, and for each 5-year incremental increase in age, the likelihood that women would report having undergone a screening mammography increased nearly 2-fold. The 2 barriers that were most commonly mentioned by women in this age group who had not undergone a mammogram in the previous 2 years were "doctor didn't order it" (31%) and "I'm too young" (30%).
In addition to older age, predictors of screening mammography among women 40 to 50 years included having a primary-care physician, having a physician recommendation, awareness of increased risk for breast cancer associated with chest radiation, increased general health concerns, and having weighed the pros and cons of mammography and deciding in favor of it. The most common barriers to screening mammography reported were "put it off" or "didn't get around to it" (27%) and "too expensive" or "no insurance/cost" (17%).
Dr. Oeffinger believes that cancer centers need to be more proactive in their follow-up. "We are working with cancer centers around the country to facilitate this process," he said. "However, not surprisingly, most adult survivors of childhood cancer are no longer followed at a cancer center, owing to reasons such as insurance, age limitations of children's hospitals, moving away from the area, and so on."
Is MRI a Better Screening Choice?
In an accompanying editorial, Aliki J. Taylor, MD, MPH, PhD, and Roger E. Taylor, MD, from the University of Birmingham, in the United Kingdom, point out that repeat mammograms carry their own risk. 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," they write. "This is an important question that needs to be addressed in future studies."
Another concern is that the efficacy of standard mammography in detecting preinvasive and malignant lesions is relatively poor in young women because of the density of breast tissue. Guidelines from the Children's Oncology Group recommend breast MRI as an adjunct to mammography, and the editorialists write that future studies should explore the role of MRI as a replacement for mammography in this population.
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