IMRT superior to CRT, possibly to proton beam for prostate cancer

2012 ASCO Genitourinary Cancers Symposium

Patients treated with intensity-modulated radiation therapy for prostate cancer had less recurrence and fewer adverse effects compared with conventional conformal radiation therapy, according to results from a comparative effectiveness study of patient records collected in the SEER database from 2002 to 2009.

Ronald Chen, MD, MPH, assistant professor of radiation oncology at the University of North Carolina at Chapel Hill, said proton beam therapy, a newer and much more expensive treatment, did not appear to improve outcomes compared with IMRT.

Compared with IMRT, patients who underwent proton beam therapy were more likely to experience rectal bleeding (17.8 vs. 12.2) per 100 person-years of follow-up. Slightly fewer patients treated with proton beam needed additional cancer treatments, although the difference was not significant (1.9 vs. 2.2; P=.24).

Chen discussed the results at a press conference in advance of the 2012 ASCO Genitourinary Cancers Symposium.

“Currently, there is no clear evidence that proton therapy is better than IMRT,” he said. “Further comparative effectiveness research is needed to further examine the patient outcomes of proton radiation vs. IMRT. There are currently two studies, a prospective cohort study in North Carolina and a planned randomized trial comparing IMRT to proton therapy in prostate cancer, and these two studies may be able to provide further insight into the comparative effectiveness of different treatments for prostate cancer.”

Use of IMRT increased from 0.15% of patients to 95.9% during the study period. Chen and colleagues analyzed records of more than 12,000 men treated with IMRT, conformal radiation therapy (CRT) or proton beam for rates of morbidity and percent of patients who needed additional treatment.

After adjusting for demographic, disease and institutional characteristics, Chen and colleagues determined that IMRT was associated with 9% fewer gastrointestinal problems and 22% fewer hip fractures compared with CRT per 100 person-years of follow-up. They also found that IMRT patients were 19% less likely to require additional cancer treatments (RR=0.81).

“This study supports use of IMRT as the current standard radiation technique for prostate cancer,” Chen said. “IMRT causes fewer side effects and achieves better cancer control compared to the older conformal radiation.” – by Jason Harris

For more information:

• Chen R. #3. Presented at: ASCO Genitourinary Cancers Symposium; Feb. 2-4, 2012; San Francisco.

Disclosure: Dr. Chen reports no relevant financial disclosures.

Anthony L. Zietman

I’m not surprised. When new technologies are introduced, we don’t know they’re going to be better. We hope they’ll be better, but they might be the same as existing technologies, and they might even be worse. This study has its limitations and is not the final answer. The researchers used the SEER database, and there are limitations with this database, but the very fact that there appeared to be a higher risk for rectal bleeding is a concern and just supports the need for more research. We cannot make assumptions of superiority when new technologies are introduced; we have to test new technology the same way we test new drugs. There are plenty of areas where proton beam is a vastly superior treatment and where due diligence has been done. The problem is that there was a rush to use it in prostate cancer without the necessary proof of superiority.

Anthony L. Zietman, MD
Jenot and William Shipley Professor of Radiation Oncology at Harvard Medical School

Disclosure: Dr. Zietman reports no relevant financial disclosures.

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