Anthony L. Zietman, M.D., of Massachusetts General Hospital and Harvard Medical School, Boston, and colleagues conducted a study to determine whether tumour control could be improved in patients with prostate cancer, including those with low-risk disease, by the use of higher radiation doses.

The study included 393 patients with stage T1b through T2b prostate cancer and prostate-specific antigen (PSA) levels less than 15 ng/mL. The median value for PSA levels was 6.3 ng/mL, and the median follow-up time was 5.5 years. Patients received either external beam radiation to a total dose of either 70.2 Gy (conventional dose) or 79.2 Gy (high dose). This was delivered using a combination of conformal photon and proton beams.

The researchers found that the proportions of men free from biochemical failure (increasing PSA level) at five years were 61.4 percent for conventional-dose and 80.4 percent for high-dose therapy, a 49 percent reduction in the risk of failure. The advantage to high-dose therapy was observed in both the low-risk and the higher-risk subgroups (risk reduction, 51 percent and 44 percent, respectively).

There has been no significant difference in overall survival rates between the treatment groups. Only one percent of patients receiving conventional-dose and two percent receiving high-dose radiation experienced acute urinary or rectal problems of Radiation Therapy Oncology Group (RTOG) grade 3 or greater. So far, only two percent and one percent, respectively, have experienced late problems having RTOG grade 3 or greater.

“This randomised trial shows that when men with clinically localized prostate cancer are treated with high-dose rather than conventional-dose external radiation therapy, they are more likely to be free from an increasing PSA level five years later and less likely to have locally persistent disease,” the authors conclude.; Source: American Medical Association (AMA)