Chest radiation increased breast cancer risk in women who survived childhood cancer

Women who survived childhood cancer but received moderate-to high-dose chest radiation as part of their treatment are at an increased risk for breast cancer at a young age.

Researchers assessed breast cancer risk and surveillance after chest radiation for childhood cancer in women aged 30 years or younger. Data were pooled from several studies conducted between 1966 and 2008 that answered at least one of three questions:

l What is the incidence and excess risk for breast cancer in women after chest radiation for pediatric or young adult cancer?

l For these women, are the clinical characteristics of breast cancer and the outcomes after therapy different from those of women with sporadic breast cancer in the general population?

l What are the potential benefits and harms associated with breast cancer surveillance among women exposed to chest radiation?

Eleven retrospective cohort and three case-controlled studies were identified. Seven thousand women received chest radiation — 422 women later developed breast cancer.

Three studies reported on clinical characteristics for breast cancer after chest radiation for childhood cancer and five studies included women with breast cancer after Hodgkin lymphoma diagnosis. There were 453 cases of breast cancer among 400 women included in these eight studies.

Overall standardized incidence ratios of breast cancer were between 13.3 and 55.5 per 10,000 person-years. These women had an absolute excess risk for breast cancer ranging from 18.8 to 79 per 10,000 person-years.

Studies indentified breast cancer in a survivor as early as eight years after chest radiation. The cumulative incidence for breast cancer by age 40 to 45 years ranged from 13% to 20%. After 25 to 30 years of follow-up, the incidence was between 12% and 26%. Researchers said this increased risk is similar to that seen in women with BRCA gene mutations.

Henderson TO. Ann Intern Med. 2010; 152:444-455.