A single case of diagnosed breast-cancer can be due to multiple causes, each of which contributed. Not a suspected cause. Medical uses are sometimes very beneficial. The key point is that women can receive all the benefits of medical radiation with vastly less harm , if the medical professions will reduce unnecessarily high dose-levels and frequencies of exposure. If a child and an adult receive equal radiation doses, they both acquire an increased risk of cancer.
Every exposure adds to a population's rate of cancer.