Dr. William U. Shipley, chair of the genitourinary oncology unit at the Massachusetts General Hospital in Boston, one of two institutions spearheading the randomized trial of protons vs. IMRT, noted the apparent reluctance of proton centers to participate.
"We are opening that trial, and we will be joined, surprisingly, by as many as 5 of the 25 centers in the United States. For some reason, the other 20 feel that they don’t want to test the protons," he commented. "But we are, and I assure you that it will give you whatever information we have."
Surgery and Brachytherapy Top EBRT
In the second study, Dr. Jay P. Ciezki of the Cleveland Clinic and colleagues, analyzed data for 137,427 men with prostate cancer of various stages diagnosed in 1991-2007 who received single-modality therapy.
The lengthy study period is important because patients are unlikely to die of prostate cancer, whereas morbidity may become problematic with time, he said. "It’s really of great interest to all of us who treat prostate cancer what happens after that 5-year mark."
With a median duration of follow-up of 5.9 years, the overall rate of toxicity requiring intervention, as determined from billing codes, was higher for men treated with EBRT (8.8%) than for their counterparts treated with prostatectomy (6.9%) or brachytherapy (3.7%). The most common gastrointestinal toxicity by far was rectal bleeding that required cauterization, whereas the most common genitourinary toxicity was urinary stricture requiring dilation.
The cumulative incidence of gastrointestinal and genitourinary toxicity with EBRT continued to rise over the 17-year period, whereas it generally plateaued for the other two modalities after the first 5 years. When the external beam group was stratified by radiation technique, the late rise in genitourinary toxicity seemed to be largely driven by IMRT.
EBRT was also the most expensive of the three modalities, Dr. Ciezki reported. When both the initial treatment and the treatment of any toxicity were considered, the mean total cost per patient per year was $6,412 – twice that for open prostatectomy, at $3,206, and more than twice that for brachytherapy, at $2,557 (P less than .0001).
Based on these data, "the long-term toxicity and cost per patient-year of the major prostate cancer treatment modalities [differ], with the external beam being the most toxic and the most costly," he commented.
Dr. Nguyen noted that it is unclear from the study whether EBRT should be abandoned for patients with low-risk disease, given factors such as potential confounding and the big improvement in the targeting of EBRT during the study period, so that the results might not reflect what is done today.
"Further prospective or randomized trials are needed to try to separate the effects of the treatment from the effects of patient selection," he concluded. "But if this study is confirmed in other large studies, this could provide a societal and clinical rationale to favor brachytherapy over external beam in men who qualify for both."
The symposium was sponsored by the American Society for Clinical Oncology, the American Society for Radiation Oncology, and the Society of Urologic Oncology.
Dr. Sheets and Dr. Ciezki disclosed that they had no relevant conflicts of interest. Dr. Nguyen disclosed that he receives research funding from Varian.