The first-ever study to analyze 25 years of follow-up data after radiation therapy (RT) treatment for prostate cancer patients has found the treatment controls disease effectively long-term, and if prostate specific antigen (PSA) is less than 0.2 ng/ml at 15 years post-treatment, later recurrence is very unlikely.
Results of the study, which was conducted by four physicians from Radiotherapy Clinics of Georgia in Atlanta, were published in the March issue of the Journal of Urology.
“With this irradiation program, cancer control, defined using the recurrence definition for radical prostatectomy, was durable with no further recurrence between 15.5 and 25 years of follow up,” wrote Frank A. Critz, MD, and colleagues. “This study also suggests that at least 15 years of follow up are necessary to fully evaluate any prostate cancer treatment.”
The authors gathered data from 3,546 consecutive patients who were treated with I-125 prostate implants followed by external beam irradiation between 1984 and 2000. Median follow-up was 11 years.
The disease-free survival rate 25 years after irradiation was 75 percent, according to Critz and colleagues. A majority of recurrences occurred within the first five years, and the longest time to recurrence was 15.5 years. In the men with recurrence, 5 percent of recurrences occurred after 10-year follow up.
“Intuitively, one might expect late [prostate cancer] recurrence to have a subsequent indolent course,” wrote the authors. “However, three of the 31 men (10%) with late recurrence required hormones within 36 months of recurrence (all had PSA 0.1 ng/ml or less 6 to 12 months before recurrence) and bone metastases developed in two. Thus, although findings are based on few observations, some men will have aggressive late recurrence.”
Critz and colleagues compared the results to previous prostatectomy studies that analyzed 15 years of follow up and found similar disease-free survival rates with both radiotherapy and radical prostatectomy.
A subset of patients treated since 1995 were given transperineal implants, as opposed to the previously used retropubic implants, and 15-year disease-free survival in this group was 79 percent.
For more on prostate cancer, please read “Prostate Cancer: In the eye of the storm” from Health Imaging magazine.