Radiotherapy Your child may have radiotherapy in the location of the original (primary) tumour to ensure any cancer cells remaining from induction chemotherapy, surgery and high-dose chemotherapy are killed off. The goal is to reduce the chances of the cancer coming back in that area. It uses high energy x-rays to kill the cancer cells in daily fractions over the course of three to five weeks. It's administered using a radiotherapy machine and your child won't feel anything during treatment. There are some short-term side-effects like possible skin reactions, nausea/diarrhoea and tiredness.