Prostate cancer patients administered high doses of proton-beam therapy appear to have a markedly reduced risk of disease recurrence when compared with other low-risk patients treated with conventional radiation therapy, according to two recent studies.
“At 10 years after treatment, 93% of low-risk patients treated with high-dose radiation were free of prostate cancer, compared with 69% of patients who had conventional doses,” said Carl Rossi, Jr., MD, lead author of one study. That difference reached statistical significance (P < .0001), added Dr. Rossi, who is an associate professor of radiation medicine at Loma Linda University in Loma Linda, Calif.
In a second study, which specifically scrutinized outcomes to measure adverse events with use of the proton boost regimen, researchers again found that the treatment proved safe.
“There was minimal early genitourinary [GU] and gastrointestinal [GI] toxicity in the prospective trial with proton therapy,” said principal investigator Nancy Mendenhall, MD, professor and chair of radiation oncology at the University of Florida in Gainesville and Jacksonville.
No trade-off between dose and quality of life
“This first of its kind study provides evidence of the benefits of giving high radiation doses to low- and intermediate-risk prostate cancer patients,” Dr. Rossi said. “Delivering higher doses with proton-beam therapy is safe, effective, and has minimal side effects.”
In addition, Dr. Rossi said there were no significant differences between the groups in changes in urinary or bowel functions, indicating that the higher-dose treatment did not come with a cost in quality-of-life issues.
The researchers enrolled patients with stage T1b or T2b prostate cancer and a prostate specific antigen (PSA) level of 15 ng/mL or less. These patients were randomized to receive a boost to the prostate alone using conformal protons of either 19.8 or 28.8 Gy equivalent (Gye). All patients then received 50.4 Gy at 1.8 Gy per fraction using three-dimensional conformal photons to the prostate, seminal vesicles, and periprostatic tissues. No patient received androgen suppression with their radiation therapy (ASTRO 2009 abstract 22).
Of the 393 eligible patients, 197 received the conventional dose of 70.2 Gye and 196 received a high dose of 79.2 Gye. The median follow up was 8.9 years.