The addition of radiation therapy to hormone therapy extends survival of men with locally advanced high-risk prostate cancer vs hormone therapy alone, according to a phase III trial reported at the 2010 ASCO Annual Meeting.¹ These findings are especially important, because many urologists and oncologists question the use of radiotherapy in this setting, said the lead investigator.

"This study challenges oncologists' perceptions about radiation therapy [in high-risk prostate cancer]," stated Padraig Warde, MBChB, who is Deputy Head of the Radiation Medicine Program at the University of Toronto's Princess Margaret Hospital. "These data confirm that radiation therapy should be considered as part of the package for men with high-risk prostate cancer."

"This study firmly cements radiation therapy as an indispensable part of the treatment of men with locally advanced, high-risk prostate cancer," agreed Jennifer C. Obel, MD, who moderated an official press conference at the meeting. Dr. Obel is a medical oncologist at the NorthShore University HealthSystem and Assistant Clinical Professor of Medicine, University of Chicago.

Study Data

The study population included 1,205 patients with bulky local and/or high prostate-specific antigen and/or high Gleason score. "Such patients represent 15% to 25% of all cases of prostate cancer," Dr. Warde told listeners.

Patients were randomized to continuous hormone therapy (androgen deprivation) alone or hormone therapy plus radiation to the prostate and surrounding lymph nodes. Radiation was given as 45 Gy to the pelvis (25 fractions over 5 weeks) with an additional 20 to 24 Gy to the prostate (10 to 12 fractions over 2 to 2.5 weeks). In 1999 the protocol was amended to allow treatment to the prostate alone if the treating physician felt whole pelvic radiation was inappropriate for the patient.

Baseline demographic and disease characteristics were similar between arms 1 and 2. Mean age was about 70 years, and 81% of patients had a Gleason score of 7 or less, whereas 18% had a Gleason score of 8 to 10.

After 7 years, overall survival was 74% for men treated with both hormone therapy and radiation vs 66% for men treated with hormone therapy alone (P = .0331), representing a 23% reduction in risk of death with the addition of radiation. Seven-year disease-specific survival was 90% vs 79% for the two arms, respectively (P = .001), representing a 43% reduction in the likelihood of dying from prostate cancer when radiation was added to hormone therapy.

Late severe toxicities were rare and occurred in 2.3% of each arm.

Optimal Regimen

"Even though this trial was designed in 1993, we believe it is relevant today," Dr. Warde noted.

He added that although combined-modality therapy should be considered the standard of care in this setting, the optimal duration of hormone therapy needs to be defined. "It may not be necessary to use lifelong androgen-deprivation therapy, as was used in this trial," he said.

In addition, he commented that radiation dose and techniques have changed considerably over the years, and modern radiation may be even more beneficial. ■

Reference

1. Warde PR, Mason MD, Sydes MR, et al: Intergroup randomized phase III study of androgen deprivation therapy + radiation therapy in locally advanced prostate cancer (NCIC-CTG, SWOG, MRC-UK, Int: T94-0110;NCT000026333). 2010 ASCO Annual Meeting. Abstract CRA4504. Presented June 6, 2010.