IMRT Superior to Conventional Radiotherapy in Prostate Cancer

Roxanne Nelson

February 01, 2012

February 1, 2012 — A comparative study of 3 radiotherapy approaches for the treatment of localized prostate cancer has found that the use of intensity-modulated radiation therapy (IMRT) might reduce disease recurrence and morbidity, compared with conventional conformal radiation therapy. The analysis also found that proton therapy does not significantly improve outcomes, compared with IMRT, but appears to increase the incidence of gastrointestinal (GI) events.

Many prostate cancer patients receive radiation therapy as their curative treatment, explained senior author Ronald Chen, MD, MPH, assistant professor of radiation oncology at the University of North Carolina at Chapel Hill, and research fellow at the Cecil G. Sheps Center for Health Services Research in Chapel Hill.

Older conformal radiation therapy was initially used; then came IMRT, which is a newer technology but also more costly. "Today, proton radiation is receiving a lot of attention as a new way to treat prostate cancer," said Dr. Chen, who presented the highlights of his study during a presscast in advance of the 2012 Genitourinary Cancers Symposium, being held in San Francisco, California. "It is the most expensive radiation technique today, but it is unclear if newer treatments actually improve patient outcomes; therefore, comparative research is needed."

Dr. Chen explained that over the past 10 years, IMRT has largely replaced conventional conformal radiation therapy as the main radiation technique for prostate cancer, even in the absence of strong supportive data. "Since 2000, IMRT use has increased dramatically, from essentially 0% to over 90%," he pointed out. "Corresponding with this was a decrease in the use of older conformal radiation techniques to almost 0."

More recently, there has been a rapid increase in the number of proton radiation centers built in the United States. This suggests a similar phenomenon might be unfolding with proton radiation, he said.

"However, it is not known if newer radiation techniques are better, and few studies have actually compared the outcomes of one treatment with another," Dr. Chen added.

Fewer GI Effects, Lower Recurrence With IMRT

Using the Surveillance, Epidemiology, and End Results (SEER)–Medicare linked database, Dr. Chen and colleagues analyzed data on more than 12,000 patients with localized prostate cancer who were treated with conventional conformal radiation therapy, IMRT, or proton-beam radiation from 2002 to 2007. They compared the rates of morbidity (GI, urinary, and erectile dysfunction, and hip fractures) and additional cancer therapy (surrogate for recurrence) among the 3 therapies.

After adjustment for demographic, disease, and institutional characteristics, the researchers found that men treated with IMRT were less likely than those treated with conformal radiation therapy to report GI morbidity (13.4 vs 14.7 per 100 person-years; rate ratio, 0.91; P < .001) and hip fractures (0.8 vs 1.0; rate ratio, 0.78; P = .006). However, men who received IMRT were more likely to be diagnosed with erectile dysfunction (5.9 vs 5.3; rate ratio, 1.12; P = .006).

Urinary adverse effects were nearly identical between the 2 therapies. However, patients who received IMRT were less likely to receive additional cancer therapy (2.5 vs 3.1; rate ratio, 0.81; P < .001).

No Clear Benefit for Proton Therapy

In a propensity-score-matched comparison between proton therapy and IMRT, patients who received proton therapy had a higher rate of GI morbidity (17.8 vs 12.2 per 100 person-years; rate ratio, 0.66; P < .001). There were no significant differences between proton therapy and IMRT in rates of other urinary morbidities, erectile dysfunction, or the need for additional therapies.

"This study supports the use of IMRT as the current standard radiation technique for prostate cancer," concluded Dr. Chen. It causes fewer adverse effects and achieves better cancer control than conformal radiation treatment.

"Currently, there is no clear evidence that proton therapy is better than IMRT. Further comparative-effectiveness research is needed to examine patient outcomes with proton radiation and IMRT," he said.

Dr. Chen added that 2 studies are currently ongoing — a prospective cohort study and a randomized trial comparing IMRT with proton therapy — which might provide insight into these 2 treatments for prostate cancer.

"This was a very interesting study," said Nicholas J. Vogelzang, MD, from US Oncology Research, and moderator of the presscast.

He pointed out that patients often ask about the status of proton therapy and how it compares to standard therapy. "I think that, based on these data, we can safely say that there is no clear evidence that proton therapy is better than IMRT," said Dr. Vogelzang.

"Given its cost and potentially increased toxicities, we must continue to study this modality. Hopefully, the 2 ongoing studies mentioned by Dr. Chen will be completed rapidly and give us a better cost/benefit ratio," he added.

This study was funded by the Agency for Health Care Research and Quality. The authors have disclosed no relevant financial relationships.

2012 Genitourinary Cancers Symposium (GUCS): Abstract 3. To be presented February 2, 2012.

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