Orlando, FL--Adjuvant radiotherapy for pT3 prostate cancer significantly reduces the risk of biochemical progression after radical prostatectomy with a very low rate of side effects, according to a study by German researchers. But a U.S. radiation oncologist said the findings of this and two related studies are not powerful enough to change the current standard of care.
Thomas Wiegel, MD, of the University of Ulm, Germany, reported results of a randomized phase III trial involving 385 pT3 prostate cancer patients with positive or negative surgical margins.
The study, presented at the American Society of Clinical Oncology annual meeting, was prompted by clear retrospective data that show an increase of biochemical control for 5 years in adjuvant radiotherapy for pT3 tumors.
Seventy-eight patients-45 in the radiotherapy group and 33 in the watchful waiting group-did not reach undetectable PSA levels. They were declared as having "progressive disease," and were moved to a third arm to be given radiation therapy, beginning 8 to 12 weeks after surgery. Median follow-up was 40 months for the radiotherapy recipients and 38.5 months for the watchful waiting group, with improved biochemical non-evidence of disease (BNED) as the endpoint.
Biochemical improvement At 4 years, BNED increased to 81% for the patients who had received radiation therapy, compared with 60% for those in the observation group.
"We found a significant advantage at 4 years of 20% in favor of 60 Gy radiotherapy, with biochemical progression of the disease," Dr. Wiegel said. "Outcome shows that radiotherapy is better than wait-and-see for biochemical progression using PSA, but not for overall survival. Also, randomized studies presented within the last 12 months show the same direction: better biochemical control but, for the moment, no better overall survival."
Anthony D'Amico, MD, PhD, of the Dana-Farber Cancer Institute, said the findings shown by Dr. Wiegel's group are similar to those seen in studies from the European Organization for Research in the Treatment of Cancer and the Southwest Oncology Group.
"There is a benefit in decreasing PSA failure by adding post-op radiation in pT3 patients," Dr. D'Amico said. "But none of these three studies had been sufficiently powered or had long enough follow-up to change the standard of care because none of them has yet shown a difference in the clinically relevant endpoint of survival.
"In order to get to the point where this would become adopted as a standard of practice; that is, to give radiation in the adjuvant setting after surgery for men who have extraprostatic disease, you would have to see impact, not just in a blood test, but either on the presence of bone metastasis or cancer death," he said.