By Amanda Gardner 18 feb 2009-- In an ironic testament to the success of childhood cancer treatments, researchers report that women who were treated as children with radiation for Hodgkin's disease were almost 40 times more likely to develop breast cancer later in life.
"We can cure most patients now who have Hodgkin's disease. Back in 1950, it was regarded as a universally fatal disease," said study co-author Dr. Nancy Mendenhall, a professor of radiation oncology at the University of Florida College of Medicine in Gainesville. "[But] when you've got a high cure rate, as people age, you begin to identify some of the unanticipated effects that seem to be related to the treatments. If you don't cure the patients, they don't survive to see those effects."
The risk rose with the radiation dose, and there was also a higher risk of developing malignancies in both breasts.
The findings, published in the September issue of The International Journal of Radiation Oncology Biology Physics, are part of a larger study involving 930 children treated for Hodgkin's disease between 1960 and 1990 at five U.S. centers. Overall, survivors of childhood Hodgkin's disease, especially female survivors, were found to be at higher risk for second malignancies.
Often treatment for Hodgkin's involves radiation to the breast area, so some amount of breast tissue receives some amount of radiation, explained study leader Dr. Louis S. Constine, a professor of radiation oncology at the James P. Wilmot Cancer Center, University of Rochester Medical Center.
The amounts of radiations used are much lower than in the past, Constine added, as is the proportion of the body irradiated. Chemotherapy is also sometimes substituted for radiation in more modern treatment.
This analysis followed almost 400 female survivors of childhood Hodgkin's disease for an average of almost 17 years.
Women who had had this childhood cancer were 37 times more likely to develop breast cancer as compared to women who had not had Hodgkin's disease, although the absolute risk was low (29 women overall were diagnosed with breast cancer). Women were diagnosed as early as 9.4 years after radiation and as late as 36.1 years after the initial treatment. More women are likely to be diagnosed with breast cancer as follow-up continues.
Women who were diagnosed at an earlier stage of Hodgkin's disease or were older than 12 were more likely to develop breast cancer, possibly a result of different radiation doses or the developing breast tissue being more susceptible to harm from radiation.
About one-third of women in the group had cancer in both breasts.
Radiation of the pelvic area lowered breast cancer risk, although Mendenhall speculated that this surprising finding could be due to impact on hormone production in the ovaries.
While guidelines recommend that women, in general, start getting mammograms at age 40, women who received radiation which potentially impacted breast tissue are urged to start screening 10 years after radiation or at age 30, whichever comes first.
Research released last month, however, found that almost half of female childhood cancer survivors under the age of 40 who had chest radiation as part of their treatment are not following the recommended advice to get screening mammograms sooner than other women.
It's unclear how different treatment paradigms will affect survivors.
"The majority of these patients were treated in an earlier era, and current treatment protocols are certainly much different in terms of the amount of radiation and the field size," said Dr. Rajaram Nagarajan, an assistant professor of hematology/oncology at Cincinnati Children's Hospital Medical Center. "But it will still take some time until we are able to assess how current changes are going to change these risks. The assumption is that they are going to reduce the risk."
Regardless, Nagarajan said, survivors need to receive regular care in centers and clinics specializing in the follow-up of pediatric cancer survivors.
"We have made a lot of changes in the past 10 to 15 years," he said. "The problem is, we're always five or 10 years behind in terms of assessing."