It is not yet known whether these side effects might be so harmful to the patient that a higher radiation dose is not beneficial.

Prostate-specific antigen (PSA) is a substance produced in the prostate. In men with prostate cancer, the PSA level in the blood is often elevated. After the cancer is removed, the PSA level drops.

If the PSA is seen to rise again in the follow-up tests after the prostatectomy, this indicates that cancer cells are again present in the body. Such a relapse can even occur years after the prostatectomy. If the tumor cells are found only at the site of the previous episode of prostate cancer, the treatment is irradiation of this site. 

The dosage of radiotherapy in such a situation differs from hospital to hospital. However, it is still not clear whether a higher dose of radiation is more effective than a lower one. A higher radiation dose also usually causes more side effects than a lower dose. It is not yet known whether these side effects might be so harmful to the patient that a higher radiation dose is not beneficial.

These unresolved questions were investigated in study SAKK 09/10.