Nick Mulcahy

November 09, 2012

BOSTON, Massachusetts — Patients with prostate cancer who were treated with proton-beam therapy (PBT) had better quality-of-life (QoL) scores in the first few months after treatment than those treated with 2 more common modalities, according to new research.

However, over time, the QoL scores of those treated with PBT were similar to the scores of those treated with 3D conformal (3D-CRT) or intensity-modulated radiation therapy (IMRT), according to a study presented here at the American Society for Radiation Oncology 54th Annual Meeting.

The study looked at QoL scores for 2 measures: patient-reported bowel and urinary function. The authors, led by Phillip J. Gray, MD, from the Harvard radiation oncology program in Boston, Massachusetts, used data from 3 different patient cohorts because there has been no direct comparison of PBT, 3D-CRT, and IMRT.

Dr. Gray and colleagues reviewed the outcomes of 370 patients: 94 treated with PBT at Massachusetts General Hospital in Boston; 123 treated with 3D-CRT at hospitals affiliated with Harvard University; and 153 treated with IMRT who were part of the Prostate Cancer Outcomes and Satisfaction With Treatment Quality Assessment consortium.

At 2- to 3-month follow-up, patients treated with PBT reported minimal diminishment in bowel function, whereas patients treated with 3D-CRT or IMRT reported modest but "clinically meaningful changes" in bowel function, Dr. Gray reported during a meeting press conference.

However, at 1 and 2 years, patients in all 3 groups reported clinically meaningful decrements in bowel function. The decline just took longer to develop in the PBT group.

At 2- to 3-month follow-up, urinary QoL scores were lower than they were at baseline in all 3 groups; however, these changes were only clinically meaningful in the IMRT group. At 12 months, there was also a clinically meaningful decrement in urinary QoL scores in the PBT group. Again, the adverse event took longer to develop in the PBT group. At 2 years, the QoL scores had returned to near-baseline levels in all 3 groups, leaving a minimal — and not clinically meaningful — loss of function.

The 3 modalities have "distinct patterns of toxicity," Dr. Gray noted about this mishmash of data.

These are "exactly the kind of data we need," said press conference moderator Colleen Lawton, MD, from the Medical College of Wisconsin in Milwaukee, about the comparison of the radiation methods. "We certainly know [that PBT is] more costly," she noted.

Median patient age was 64 years in the PBT group, 70 years in the 3D-CRT group, and 69 years in the IMRT group. Treatment dose ranged from 74.0 to 82.0 Gy relative biologic effectiveness in the PBT group, from 66.4 to 79.2 Gy in the 3D-CRT group, and from 75.6 to 79.2 Gy in the IMRT group.

Patients treated with IMRT and PBT were assessed using the Expanded Prostate Cancer Index Composite (EPIC) instrument. Patients treated with 3D-CRT were assessed using the Prostate Cancer Symptoms Index (PCSI); these scores were converted to match those of the EPIC scale.

Clinically meaningful differences in QoL scores were defined as those exceeding half the standard deviation of the mean baseline score.

"Our study provides a unique addition to existing research in this field and suggests that patients undergoing proton-beam therapy for prostate cancer may experience fewer immediate side effects," said Dr. Gray.

A prospective randomized controlled trial to further investigate differences between radiotherapy modalities is now underway at the Massachusetts General Hospital and the University of Pennsylvania in Philadelphia. The trial will compare PBT and IMRT for patients with localized prostate cancer and is expected to open at several other proton centers next year.

The authors have disclosed no relevant financial relationships.

American Society for Radiation Oncology (ASTRO) 54th Annual Meeting. Abstract LBA1. Presented October 29, 2012.