The American Society of Radiation Oncology's (ASTRO) annual meeting, held last week in Boston, was a testament to the growing body of evidence supporting proton beam therapy for the treatment of men with prostate cancer.

Several studies were presented at the conference that assessed prostate cancer patients' quality of life and toxicities following treatment with proton beam therapy. All of the studies reported favorable outcomes, especially for safeguarding men's bowel and urinary functions.

Quality of life

One of the larger data sets presented was a multi-institutional study of 1,090 men treated at the MD Anderson Proton Therapy Center, Scripps Proton Therapy Center, Loma Linda Medical Center, Massachusetts General Hospital, and the University of Florida Proton Therapy Institute. It found that patient-reported quality of life scores equaled healthy men. Patients, who averaged 65 years old, completed the Expanded Prostate Cancer Index Composite (EPIC) survey up to 10 years following proton beam therapy treatment. Prostate cancer patients scored 89.8 for urinary quality and 92.7 for bowel functions, compared with scores of 89.5 and 92.4, respectively, for healthy men. The survey used a scoring system of 1 (poor) to 100 (perfect).

Another study compared quality of life scores from prostate cancer patients who received proton beam therapy to those who were treated with two other common radiation therapy modalities: intensity modulated radiation therapy (IMRT) and 3-D conformal (3-D CRT). One of the main takeaways from this study, authors concluded, was that proton beam therapy appeared to be associated with better early bowel quality of life compared to 3D-CRT and IMRT. The study evaluated 123 patients treated with 3D-CRT from 1994-2000 at Harvard Affiliated Hospitals; 153 patients treated with IMRT from 2003-2006 at 9 hospitals; and 94 patients treated with proton beam therapy from 2004-2008 at Massachusetts General Hospital.

ProCure's findings

While all studies to date on the effectiveness of proton beam therapy treatment have been conducted at academic medical centers, the for-profit chain ProCure, which has been opening centers around the country, has also been compiling evidence for proton beam therapy. The first ProCure center opened in Oklahoma City in 2009, and from day one, it established a patient database and opened a registry study.

Dr. Sameer Keole, a radiation oncologist at ProCure Proton Therapy Center in Oklahoma City, presented results from 76 prostate cancer patients who were treated at the facility.

Patients at ProCure completed EPIC surveys and results were similar to the other studies with prostate cancer patients treated with proton beam therapy in that they showed positive quality of life scores and reduced side effects for patients. Men reported urinary and bowel quality of life satisfaction scores identical to those recorded before their treatment.

"The fact that we are a community-based proton center is unique to the growing body of evidence," Keole told DOTmed News.

A complement to all the studies was a three-year analysis of toxicity outcomes in two prospective trials of image-guided proton therapy for early and intermediate-risk prostate cancer, presented by Dr. Nancy Mendenhall, medical director of the University of Florida Proton Therapy Institute. In the study, toxicity rates were scored and disease was assessed in 171 men who were followed for a minimum of five years. This study was able to more clearly define a relationship between toxicity and volume with the hope of providing dose-constraint guidelines for other proton therapy centers to help them achieve better results.

Proton therapy is still small but growing

According to Leonard Arzt, executive director of the National Association for Proton Therapy, who also attended the conference, there was more attention paid this year at ASTRO than in years past to proton beam therapy "in terms of presenters and poster sessions."

Proton beam therapy only makes up 1 percent of all radiation oncology procedures, but experts say it's expected to grow to 5 percent over the next five years. The high cost of building a facility has always been an obstacle. Currently there are 10 facilities operating around the country, twice the number in 2006. Ten more are under construction or in development to provide cancer treatment to patients nationwide. In addition, the industry has been working to reduce the costs associated with the treatment. One example is the smaller footprint proton therapy unit from Mevion Medical Systems Inc. that received Food and Drug Administration approval in June.

"At this point, it's very expensive, but I think over the next 10 years the price will come down and [reports on] its efficacy will prove its value even more," said Keole.