San Francisco, CA—A new, large comparative effectiveness analysis of 3 techniques for delivering radiation therapy for the treatment of localized prostate cancer supports intensity-modulated radiation therapy (IMRT) as the current standard, said Ronald Chen, MD, MPH, Assistant Professor of Radiation Oncology, University of North Carolina (UNC), Chapel Hill, and Research Fellow, Sheps Center for Health Services Research, UNC at the 2012 annual Genitourinary Cancers Symposium.
Men treated with IMRT were less likely to have cancer recurrence or significant adverse effects than those who received conventional conformal radiation therapy (CRT).
The analysis also revealed no advantage with proton beam radiation, the newest and costliest radiation technique, over IMRT.
“Proton radiation is receiving a lot of attention as a new way to treat prostate cancer, and it is the most expensive radiation technique to date,” said Dr Chen. “However, it is unclear if new treatments actually improve patient outcome, and, therefore, comparative effectiveness research is needed.”
Since 2000, the use of IMRT has increased dramatically, from essentially 0% to 96%, practically replacing the older CRT.
“More recently there has been a rapid increase in the number of proton radiation centers built in the United States, suggesting that a similar phenomenon may be seen with an increased use of proton radiation in the near future,” Dr Chen said.
Dr Chen and colleagues analyzed data from the Surveillance, Epidemiology, and End Results (SEER)-Medicare database of more than 12,000 patients with localized prostate cancer who received 1 of the 3 forms of radiation therapy between 2002 and 2007.
The number of patients in each group who required additional cancer treatments after radiation was used as an indicator for cancer recurrence. Compared with patients who received CRT, those who received IMRT suffered fewer bowel adverse events. The rates of bowel adverse events were 14.7 events per 100 patient-years for CRT versus 13.4 events per 100 person-years for IMRT, corresponding to a 9% relative reduction in events from IMRT.
The IMRT group also had 22% fewer hip fractures than the CRT group, although hip fractures were a very uncommon event after radiation (0.8 events per 100 patient-years in the IMRT group vs 1 event per 100 patient-years in the CRT group).
Patients who received IMRT also required 19% fewer additional cancer treatments than those who received CRT, “suggesting that there’s better cancer control with IMRT,” said Dr Chen. However, the IMRT group had a relative increase of 12% in the frequency of erectile dysfunction versus CRT—5.9 events versus 5.3 events per 100 patient-years, respectively.
Compared with IMRT, patients who received proton beam therapy had a 66% higher rate of bowel side effects: 12.2 events per 100 patient-years versus 17.8 events, respectively.
There was no significant difference between IMRT and proton therapy in the rates of other adverse effects and additional cancer treatments.
“This study supports the use of IMRT as the current standard radiation technique for prostate cancer,” said Dr Chen. “IMRT causes fewer side effects and achieves better cancer control compared with the older CRT. Currently, there is no clear evidence that proton therapy is better than IMRT.”
Two additional comparative effectiveness studies of radiation therapy technique in patients with prostate cancer are ongoing.
