ORLANDO — Adjuvant radiotherapy following prostate cancer surgery significantly improved overall and metastatic disease-free survival, compared with surgery alone, according to 12-year results of an ongoing, randomized prospective study.
Adjuvant radiotherapy also increased biochemical control, avoided the need for androgen ablation, decreased detectable local failures, and decreased metastatic disease.
“It improved every parameter of which we know,” Dr. Gregory Swanson said during a late-breaking science forum at the annual meeting of the American Urological Association.
Dr. Swanson and fellow researchers with the Southwest Oncology Group (SWOG) Genitourinary Committee assessed 425 men with pathology-proven pT3 prostate cancer. All of the men had surgical margins positive for cancer following radical prostatectomy, placing them at high risk for recurrence. The mean age was about 65 years. Radiotherapy was 60–64 Gy directed at the prostate fossa.
A total of 214 men were randomized to surgery and radiation and 211 received surgery alone. Median follow-up is now longer than 12 years, said Dr. Swanson of the departments of radiation oncology and urology at the University of Texas at San Antonio.
Previously reported, 10-year median follow-up results showed significantly improved biochemical control and decreased local failure in the radiation group, but only a trend toward improved metastatic-free and overall survival.
“Metastatic-free survival is now statistically significant. So the finding is positive that radiation does improve metastasis-free survival for high-risk patients,” Dr. Swanson said.
The 15-year metastatic-free survival is 46% in the radiation group, compared with 38% in the observation group (hazard ratio, 0.74). The 15-year overall survival rates were similar—47% in the radiation group, compared with 37% in the observation group (HR, 0.76).
However, the trade-off for improved outcomes was greater morbidity in the adjuvant radiotherapy group, Dr. Swanson reported. A review of records showed that urethral stricture occurred in 38 patients (18%) in the radiation group, compared with 20 patients (10%) in the observation group.
Likewise, incontinence occurred more often in the radiation group (14 patients, 7%) than it did in the observation group (6 patients, 3%). Proctitis occurred in seven patients (3%) of the radiation group but in none of the observation group.
The SWOG researchers also tracked complications prospectively. Compared with baseline, they found that there was a significantly higher rate of complications at 6 weeks in the radiation than in the observation groups. For example, 71% of patients in the radiation group and 43% of the patients in the observation groups reported an unpleasant quality of life; 37% and 18%, respectively, reported increased urinary frequency; and 59% and 7%, respectively, reported bowel tenderness.
At 2 years' follow-up, only increased urinary frequency (24%, compared with 13%) and bowel tenderness (19%, compared with 4%) remained significantly more common in the radiation group.
At 5 years, complications were no longer significantly different between groups. “There is increased morbidity, but it's manageable and reduces over time,” Dr. Swanson said.
On the basis of these findings, adjuvant radiotherapy should be offered to all high-risk postsurgery patients, he said. “We can significantly reduce recurrence by all parameters with adjuvant radiation.”
A meeting attendee asked if any patients opted out of radiation therapy. “There were four in each arm who did not get the treatment they were assigned to,” Dr. Swanson said.
Another attendee asked if postoperative prostate-specific antigen levels were 0 in all patients after surgery. Dr. Swanson replied that 98% were below 1.0 ng/mL.
“But you are right—not all were 0 PSA.” The investigators previously reported that adjuvant radiation reduces the risk of biochemical failure at all postsurgical PSA levels at a follow-up of 10 years (J. Clin. Oncol. 2007;25:2225–9).