How long does external radiation continue to work after treatment has ended?

External radiation therapy continues to affect cancer cells for some time after treatment has ended, typically for days to weeks. The radiation damages the DNA of cancer cells, leading to cell death, which can occur even after the radiation exposure has stopped. Patients may notice the effects of treatment, including side effects, for several weeks as the body continues to respond to the radiation. However, the precise duration can vary depending on the individual and the specific treatment regimen.