 Radiotherapy is used when drug treatment is failing to control the pain of a growing tumor, such as in bone metastasis (most commonly), penetration of soft tissue, or compression of sensory nerves.Often, low doses are adequate to produce analgesia, thought to be due to reduction in pressure or, possibly, interference with the tumor's production of pain-promoting chemicals.Radiopharmaceuticals that target specific tumors have been used to treat the pain of metastatic illnesses.