Proton Therapy No Better than IMRT for Prostate Cancer

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Jay P. Ciezki, MD
Jay P. Ciezki, MD

SAN FRANCISCO—Two studies comparing various treatment modalities for prostate cancer (PCa) could help doctors and patients make more informed treatment decisions, according to presentations at the 2012 Genitourinary Cancers Symposium.

In one study, investigators led by Ronald C. Chen, MD, Assistant Professor of Radiation Oncology at the University of North Carolina in Chapel Hill, found that proton therapy is no better than intensity modulated radiotherapy (IMRT) as a treatment for localized PCa, and it is associated with greater gastrointestinal (GI) toxicities. The other study, led by Jay P. Ciezki, MD, a staff member of the Department of Radiation Oncology at Cleveland Clinic, demonstrated that brachytherapy is less toxic and less costly than either external beam radiotherapy (EBRT) or either radical prostatectomy (RP).

Proton therapy

“Today, 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 lead investigator Ronald C. Chen, MD, Assistant Professor of Radiation Oncology at the University of North Carolina in Chapel Hill. The number of proton radiation centers has been increasing rapidly in the United States despite no evidence of proton therapy superiority over IMRT, he added.

The study also showed that IMRT is superior to conformal radiation therapy (CRT) in terms of adverse effects and cancer control.

To compare treatment-related toxicities and cancer control among the three radiotherapy modalities, the researchers analyzed data from the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked database for patients with non-metastatic PCa. Using prospensity-score analysis to adjust for patient characteristics, the researchers found that IMRT patients had a 34% decreased risk for bowel morbidity than patients who underwent proton therapy. The study revealed no significant difference in the need for additional cancer treatment, which the investigators used as a surrogate for cancer recurrence.

In a propensity-score adjusted analysis, IMRT patients had a significant 9% decreased risk of bowel morbidity and a 22% decreased risk of hip fractures compared with CRT patients, Dr. Chen said. IMRT, however, was associated with a significant 12% increased risk of erectile dysfunction (ED). IMRT patients had a significant 19% decreased risk of receiving additional cancer treatments.

Dr. Chen concluded that the study, which was funded by the federal Agency for Healthcare Research and Quality, “supports the use of IMRT as the current standard radiation technique for prostate cancer. IMRT causes fewer side effects and achieves better cancer control compared to the older conformal radiation technique. Currently, there is no clear evidence that proton therapy is better than IMRT.” Additionally, Dr. Chen noted that additional comparative effectiveness studies are needed to directly compare patient outcomes of proton therapy versus IMRT.

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