Identification of risk factors for breast cancer among women who were treated for cancer as children will improve risk stratification for this growing population of young women, according to an article in the October 19th issue of the Annals of Internal Medicine.

“We’ve known for many years that childhood cancer survivors have higher rates of breast cancer than the general population,” said lead author Lisa Kenney, MD, of Dana-Farber Cancer Center and Children’s Hospital. “But, other than prior treatment with chest radiation, it hasn’t been clear what factors increase survivors’ risk for the disease.”

Kenney and her colleagues analyzed data from the Childhood Cancer Survivor Study −a national study of children diagnosed with cancer from 1970-1986 and who survived at least five years after treatment − for clues to the development of adult breast cancer. Of the more than 6,000 young women participating in the study, investigators identified 95 who were diagnosed with breast cancer.

As expected, breast cancer was more prevalent than normal among survivors who had been treated with chest radiation during childhood or adolescence. Breast-cancer rates were also elevated among women who had survived bone or soft-tissue sarcomas but had not received chest radiation. In addition, survivors with a family history of breast cancer had higher breast-cancer rates as well, regardless of whether they had or had not received radiation therapy as children.

“Clearly, girls treated with chest radiation are not the only survivors of childhood cancer who are at increased risk for breast cancer,” Kenney noted. “What we’ve learned from this study suggests that some survivors have a genetic tendency to developing breast cancer as young women.”

The researchers also found that women who had received pelvic radiation for childhood cancer had lower breast cancer rates, on average, than women in the general population. Researchers explained this pattern by noting that pelvic radiation can significantly decrease the ovaries’ production of estrogen. Women treated with chest radiation who later developed thyroid disease were also found to have higher rates of breast cancer.

“Physicians should make a point of assessing breast cancer risk in all young women who are survivors of childhood cancer,” commented senior author Lisa Diller, MD, of Dana-Farber and Children’s Hospital. “By offering early screening to survivors at increased risk, we can increase the chances that breast tumors will be detected and treated at the earliest stages, when they are most susceptible to therapy.”