Another study delves into the Childhood Cancer Survivors Study (CCSS) cohort and uses their big numbers to find a small signal. In particular, female survivors are at a higher risk of breast cancer at a young age than their siblings even when they receive no radiotherapy. Although the standardized incidence ratio (similar to relative risk) is high at 4.0 compared to the general population, the absolute risk by age 45 is 1.2% in survivors. The biggest risk factors for developing breast cancer were initial diagnosis of ALL or sarcoma and higher doses of alkylators or anthracyclines.
* This study should make us think about how we follow up our survivors. The findings seem to draw attention to high doses of anthracyclines and alkylators as risk factors and this is physiologically plausible. However, breast cancer at a young age is a criterion for Li Fraumeni syndrome and since sarcoma and hypodiploid ALL are also part of this disease it needs to be considered as a possible explanation. It’s also important to bear in mind that sarcoma patients get some of the highest doses of anthracyclines and alkylators introducing a confounder.