Figure 1. Schematic of radiation dose-effects on breast-cancer risk in the contralateral breast of breast cancer patients.

The overall cancer risk is determined by a balance between killing of pre-existing pre-malignant cell clones vs. induction of new pre-malignant cell clones by radiation. The hypothesis underlying the present work is that there is a dose “window” at intermediate doses where killing of pre-existing pre-malignant clones dominates, thus reducing overall cancer risks.