How does Radiation help cancer?

It doesnt it gives u lukemia

Radiation prevents cells from replicating. Since cancer cells typically replicate at a faster pace, it affects them directly. Most cells in our body do no replicate past the growing stage. There are some that do – skin, cells in outer layer of stomach and bone cells. It affects these cells too, hence, people loose their hair, have digestive problems and skeletal issues when on radiation therapy.