放射疗法（radiotherapy）是一种癌症治疗方法，它使用高剂量的放射线杀死癌细胞并阻止它们扩散。在低剂量下，辐射被用作 X 射线来查看您的身体内部并拍摄图像。

放射治疗不会立即杀死癌细胞。在癌细胞开始死亡之前需要数天或数周的治疗。在那之后，癌细胞在放射治疗结束后持续死亡数周或数月。

放射治疗可以是外照射（当您体外的机器将放射线对准癌细胞时）或内照射（当放射线放在您的体内、癌细胞内或附近时）。

Radiation therapy (radiotherapy) is a cancer treatment that uses high doses of radiation to kill cancer cells and stop them from spreading. At low doses, radiation is used as an x-ray to see inside your body and take images.

Radiation therapy does not kill cancer cells immediately. It takes days or weeks of treatment before cancer cells start to die. After that, cancer cells keep dying for weeks or months after radiation therapy end.

Radiation therapy can be external beam (when a machine outside your body aims radiation at cancer cells) or internal (when radiation is put inside your body, in or near the cancer cells).