Data Support Adjuvant Radiation Use
Gregory Swanson, MD
BOSTON—Adjuvant radiotherapy following radical prostatectomy for pT3 prostate cancer may significantly decrease the likelihood of cancer recurrence and improve metastasis-free and overall survival, according to a study.
The finding comes from an updated analysis of a Southwest Oncology Group trial designed to address whether adjuvant radiation benefits prostate cancer patients treated with radical prostatectomy. The researchers looked at patients with high-risk findings, including positive surgical margins, capsule penetration, or positive seminal vesicles.
When data from this trial were first reported, researchers had a median follow-up of 10 years. Data showed that adjuvant radiation increased biochemical control and decreased local failure but did not significantly improve metastasis-free and overall survival. Researchers now have a median follow-up of 11.5 years, during which 38 more deaths occurred.“This study is probably one of the most significant prostate cancer studies in my lifetime,” said study investigator Gregory Swanson, MD, associate professor of urology and radiation oncology at The University of Texas Health Science Center in San Antonio. “We don't have too many studies in prostate cancer that show this kind of benefit.” He reported study results here at the American Society for Therapeutic Radiology and Oncology annual meeting.
The findings have significant clinical implications, said Dr. Swanson, who presented the latest data. “Every parameter that we looked at—biochemical, local failure, metastatic disease, and overall survival—was improved after radiation,” he said. By receiving adjuvant radiotherapy, he added, men who have positive margins following surgery can cut their risk of recurrence in half, he said.
Within four months after prostatectomy, 431 men were randomized to receive adjuvant radiation or observation. Eligibility criteria included positive surgical margins, extracapsular extension, or seminal vesicle invasion with no clinical or histologic evidence of lymph node metastasis. Radiotherapy consisted of 60-64 Gy directed at the prostate fossa; between 1988 and 1997, 425 eligible men with pT3 disease were enrolled in the trial.
The observation group included 211 men (67% white, 20% black). They had a mean age of 65 years and a median follow-up of 12.5 years. The adjuvant radiation group included 214 men (72% white, 19% black) with a mean age of 64 years and a median follow-up of 12.7 years. The primary end point was metastasis-free survival.
Based on the latest data, the 15-year metastasis-free survival rate was 50% for the radiation group compared with only 38% for the observation group. The overall survival rate was 51% for the radiation group compared with 37% for the observation group. Radiation therapy significantly reduced biochemical and local failure as well as the need for subsequent androgen ablation.
With regard to complications, urethral stricture developed in 18% of the radiation group vs. only 10% of the observation group. Incontinence occurred in 7% of the radiation group compared with only 3% in the observation group. Proctitis was found in 3% of men in the radiation group but none of those in the observation group. The researchers concluded that the increased morbidity in the radiation group was manageable and that adjuvant radiation was the confirmed standard of treatment for this patient population.