Can radiation therapy cause cancer?

Secondary Cancer: Radiation does cause cancer, but is also used to treat cancer in radiation oncology. The best data for this is from children treated with radiation and followed closely for many years. The data can be murky with other causes of cancer. However, in general, the risk of secondary malignancy is much less than 1% can take up to 20 years to develop. The benefit of radiation far outweighs this risk.