Two new studies: Radiotherapy offers dividends following radical prostatectomy
Findings will impact treatment, but additional follow-up data needed
Powerful new evidence has emerged demonstrating the benefits of radiotherapy in prostate cancer patients following radical prostatectomy.
First, an update to a randomized controlled study first reported in 20061 reports that in men with at least one of three high-risk features — extra- capsular tumor extension, positive surgical margins, or seminal vesicle invasion — a course of adjuvant radiation significantly lowers the risk of recurrence. The study was conducted by Gregory Swanson, MD, a radiation oncologist and an associate professor in the departments of radiation oncology and urology at the University of Texas Health Sciences Center in San Antonio.
In addition, investigators from Baltimore, MD-based Brady Urological Institute at Johns Hopkins Medical Institutions, who are looking at prostate-cancer-specific survival in patients who have undergone salvage radiation within two years of biochemical recurrence [rising prostate-specific antigen (PSA) levels], have concluded that salvage radiation is associated with a significant increase in survival.2
Swanson's study included 425 men with aggressive prostate cancer who were randomly assigned to receive adjuvant radiation within 16 weeks of the removal of their prostate or were assigned to an observation group. Swanson reports that 46% of the patients who received radiotherapy survived at least 15 years without any evidence of the cancer spreading versus 38% of patients in the observation-only group. Further, Swanson notes that the radiotherapy reduced recurrence by all measures including biochemical, local failure, and metastatic disease.
"This was a home run," emphasizes Swanson. "There are almost no good randomized studies in prostate cancer, and here is a randomized study that was wildly positive for benefit…so it is a very important study."
Peter Rossi, MD, an assistant professor in the departments of radiation oncology and urology at Emory University School of Medicine in Atlanta, agrees that the findings are very significant. "In Swanson's study, the people with high-risk features [in the observation group] failed on average within one to two years, and radiotherapy pushed that out more than a decade," he says. "There is nothing else we can intervene with that involves just a two-month [treatment course] that is going to get us to that endpoint."
Salvage radiation boosts survival
In the study looking at the survival benefit of salvage radiation, investigators found that men whose tumors recur following prostate cancer surgery are three times more likely to survive their disease over the long term if they undergo radiotherapy within two years of the recurrence.
In the retrospective analysis, investigators reviewed the medical records of 635 men who experienced recurrent cancer following radical prostatectomy between June 1982 and August 2004. A total of 397 of the men received no salvage radiation therapy, 160 received only salvage radiation, and another 78 patients received salvage radiation and hormonal therapy. Among the men who received salvage radiation, the probability of surviving 10 years was 85%, compared with just 62% for the men who did not receive radiation.
Bruce Trock, PhD, MPH, the director of the Division of Epidemiology at Johns Hopkins Medical Institutions and the lead author of the study, says, "If our results are true, it would suggest that men with PSA doubling times of [less than] six months would benefit the most if radiotherapy is given within two years of recurrence. However, we don't know if a benefit will also emerge for men with longer PSA doubling times as longer follow-up of this cohort accrues."
Most previous studies have looked at PSA endpoints, so the fact that investigators have documented a survival benefit from salvage radiation is important, according to Ashesh Jani, MD, an associate professor of radiation oncology at Emory University School of Medicine. "It also appears to help patients who have rapid PSA doubling times, which was a subgroup that was previously thought not to benefit from radiation, so overall we are excited. And [I think] the findings will impact treatment."
Trock says he and his colleagues will continue to follow the study participants and plan to re-analyze the results in a year or two. "We are also analyzing the current data to try to identify predictors of men who have a good response to salvage radiation — those whose PSA levels go to an undetectable level — since those are the men who benefitted in our study," he says. "We also will evaluate further the issue of salvage radiation alone compared to salvage radiation plus hormonal therapy to determine whether there are some subgroups that require the addition of hormonal therapy to achieve an increased survival."
References
- Thompson I, Tangen C, Paradelo J, et al. Adjuvant radiotherapy for pathologically advanced prostate cancer. J Amer Med Soc 2006; 296:2,329-2,335.
- Trock B, Han M, Freedland S. Prostate cancer-specific survival following salvage radiotherapy vs observation in men with biochemical recurrence after radical prostatectomy. JAMA 2008; 299:2,760-2,769.
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