Is radiotherapy a good option foto prolong life?

Can be: Radiation therapy is a treatment used for treating cancer. In some circumstances, such as Hodgkin's lymphoma, prostate or breast cancer, its use in conjunction with other tools like surgery or chemotherapy, does improve cure rates for some and survival time for others. In other cases radiation is used to treat cancer symptoms, but not for a survival benefit.

Curative or useless: Do you mean radiation therapy? That's a treatment which can cure some cancers, and has no useful role in the treatment of other cancers. It all depends on what kind of cancer we're talking about, and it's stage (extent).

Yes it often is: Radiotherapy is a commonly used treatment for controlling Cancer. Depending on the extent of your cancer, with radiotherapy you have one type of treatment...other treatment may include Surgery or Chemotherapy. We often use one or more of these 3 means of treatment for Cancer.