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Proton Beam Therapy: Similar Toxicity to Standard Radiation, at Much Higher Cost

December 2012, Vol 5, No 8

The use of proton beam radiation therapy (PBRT) for the treatment of prostate cancer is increasing across the United States, but there is no evidence from randomized controlled trials to suggest that PBRT is more effective than intensity modulated radiation therapy (IMRT), which is the current standard of care. A study presented at the 2012 American Society for Radiation Oncology Annual Meeting found few differences in toxicity between the 2 techniques, but demonstrated that PBRT was associated with a 57% increase in median cost per patient.

Similar Efficacy, Double the Cost
“PBRT is an emerging treatment for men with prostate cancer, yet it is much more expensive than IMRT,” said James B. Yu, MD, Assistant Professor of Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut. “We need a prospective large study comparing radiation techniques to justify widespread use of PBRT for prostate cancer,” he explained.

The population-based, retrospective, observational study was based on 22,647 Medicare beneficiaries between the ages of 66 and 94 years who received PBRT or IMRT for prostate cancer in 2008 and 2009; 421 patients (2%) received PBRT and 27,226 patients (98%) received IMRT.

The median Medicare reimbursement per patient is $32,428 for PBRT and $18,575 for IMRT, which represents a 57% difference.

PBRT was associated with a significant reduction in urinary toxicity at 6 months versus IMRT (6.1% vs 12%, respectively); however, by 1 year, there was no difference between groups for urinary toxicity (18.9% for PBRT vs 21.9% for IMRT). No significant differences were observed at 6 months and at 1 year between the 2 groups in gastrointestinal (GI) or other toxicities.

“The longer-term effects, costs, and other clinical and patient-reported outcomes are needed to inform the adoption of PBRT for prostate cancer,” Yu stated.

The study had several limitations, he continued. It is a retrospective study that is a claims-based analysis with no staging information and with no data on the extent or field of radiation.

Potential Differences in Side Effects
A second study found minimal differences between PBRT, IMRT, and the older 3-dimensional conformal radiation therapy (3D-CRT).

The study included 153 patients treated with IMRT, 123 patients treated with 3D-CRT, and 94 patients treated with PBRT. Quality of life (QOL) was assessed by the Expanded Prostate Cancer Index Composite in the IMRT cohort and by the Prostate Cancer Symptom Index in the PBRT and 3D-CRT cohorts.

The main difference in QOL scores in the GI domain was found 2 to 3 months posttreatment, when 3D-CRT and IMRT—but not PBRT—were associated with a clinically meaningful decrement in QOL scores. Over 12 months, the 3 cohorts had similar QOL scores for GI effects.

For urinary irritation, all 3 groups had lower QOL scores at 2 to 3 months of follow-up, but this was clinically meaningful only for IMRT. Sexual function QOL scores were lower in all 3 groups at 24 months, but this was not clinically meaningful (defined in this study as scores exceeding half of the standard deviation of the baseline mean score).

“These findings are a unique addition to existing research in the field, and suggest that PBRT may lead to fewer immediate side effects in prostate cancer patients,” noted Phillip Gray, MD, a resident at Harvard Radiation Oncology Pro­gram, Boston, Massachusetts. He suggested that a prospective, randomized controlled trial is needed to compare these technologies.

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