Clinical implications arising from a recent study published in the European Journal of Cancer suggest that stereotactic body radiation therapy is effective in the treatment of prostate cancer but doses should be 47.5 Gy or lower to prevent toxicity
Stereotactic body radiation therapy (SBRT) is one method of treating men with prostate cancer (PCa), despite the lack of evidence regarding its efficacy. Using a coordinate system, it allows for the precise location of tumours. In a recent study from the European Journal of Cancer, 91 patients were enrolled in a 5 year SBRT trial. Patients were given one of three increasing doses (45 Gy, 47.5 Gy and 50 Gy) of radiation within 5 treatment sessions. The prostate was enlarged and prescription dose for different areas of the prostate were carefully controlled. Toxicity assessments, which documented bowel and bladder function, sexual function as well as quality of life, were measured at the 3 and 5 year follow-up. Gastrointestinal (GI) and genitourinary (GU) side effects, prostate specific antigens (PSA) and overall survival (OS) rates were monitored.
PSA is a protein produced by the prostate and elevated levels are associated with prostate cancer. Results show that PSA values were lowered after SBRT treatment. Overall survival rate (i.e. no occurrence of death due to any cause) was 94% at 3 years and 89.7% at 5 years with no deaths due to prostate cancer, suggesting treatment efficacy. The cancer also did not spread. GI toxicity was prevalent with the highest dose (50 Gy) of SBRT. Erectile dysfunction (ED) was reported in 25.6% of men; much more promising than previous studies. Lastly, whether the quality of life of these men was improved remains to be seen since the study was limited by low questionnaire compliance.
This study has strong clinical implications; SBRT treatments appear to be an effective way to treat prostate cancer but doses should be limited to 5 treatments at a maximum dose of 47.5 Gy, due to increased risk of toxicity associated with higher doses.
Written By: Aurelie Hartawidjojo, BSc, BScPT