Men with prostate cancer that is small and confined to the prostate gland but at risk of growing and spreading, do better if they are treated with radiotherapy combined with androgen deprivation therapy (ADT), which lowers their testosterone levels. These research findings were presented at the 33rd conference of the European Society for Radiotherapy and Oncology (ESTRO33) in Vienna, Austria.

“Although we need longer follow-up to assess the impact on these men’s overall survival, these findings need to be taken into account in daily clinical practice,” said Michel Bolla, MD, a professor of radiation oncology at Grenoble University Hospital in France. “They show that three-dimensional conformal radiotherapy, whether intensity-modulated or not, and regardless of the dose level, has to be combined with short-term androgen deprivation therapy in order to obtain a significant decrease in the risk of relapse.”

Bolla explained that these trial results indicate that this combined treatment approach should be an option proposed for men with localized prostate cancer that has an intermediate or high risk of growing and spreading.

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Bolla and colleagues from 37 centers in 14 countries recruited 819 men to a clinical trial. The patients had early stage prostate tumors, as confirmed by analyses of biopsy samples and levels of prostate specific antigen (PSA), that were at intermediate or high risk of growing and spreading to other parts of the body.

The patients were randomized to receive either radiotherapy alone or radiotherapy and two subcutaneous injections of luteinizing hormone-releasing hormone analogues (LH-RH analogues), which lower levels of testosterone to cause reversible chemical castration. Each drug injection lasted 3 months; the first was administered on the first day of irradiation and the second, 3 months later.

Doctors could choose between 1 of 3 irradiation doses: 70, 74, or 78 Gray (Gy). They followed the men for an average of 7.2 years and found that, regardless of the radiotherapy dose and whether it was intensity modulated, the 403 men who received radiotherapy combined with hormone treatment were significantly less likely to have suffered a relapse and progression of their cancer than the 407 men who were treated with radiotherapy alone. Nine men did not receive the planned treatment.

Men receiving the combined treatment had nearly half the risk (47%) of biochemical progression of their disease compared to men treated with radiotherapy only. In the combined treatment group, 118 men had a biochemical progression of their disease compared with 201 men in the radiotherapy only group.

Five years after their treatment, the men in the combined treatment group were doing significantly better. “They had better survival without biochemical progression,” Bolla said. “Among those receiving the combined treatment, 17.5% had progressed compared to 30.7% receiving radiotherapy alone.”