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NEWS & VIEWS |
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Although previous studies of salvage radiotherapy have had mixed results, principal investigator Kevin Slawin, MD, said his findings "confirm a notion that’s already been out there."
"What’s novel and important is that even men who had a short prostate-specific antigen (PSA) doubling time or aggressive high-grade disease, even a large number of those men are curable," said Slawin, a Professor of Urology at Baylor College of Medicine. "Standard belief was that those men were destined to progress, and radiation couldn’t be of help."
Mack Roach III, MD, Professor of Radiation Oncology, Medical Oncology, and Urology at the University of California, San Francisco, agreed that the benefits of salvage radiotherapy for high-grade prostate cancer are not widely appreciated.
"Some people think if you have a high-grade tumor there’s no point," said Roach, who was not involved in the study. "I’ve had patients who’ve done very well with treatment despite having high-grade tumors."
Slawin and his colleagues conducted a retrospective review of 501 men who had undergone salvage radiotherapy after radical prostatectomy, searching for clinical characteristics that might help predict which men were more likely to respond to the radiation treatments. Not unexpectedly, they found that men with lower preradiation PSA levels (below 2.0 ng/mL) and low Gleason scores (between 4 and 6) were most likely to respond to the salvage radiotherapy.
But even some men with more aggressive disease responded to the treatments, as long as they were given early in the course of the recurrence, before PSA levels had reached 2.0 ng/mL.
"The better results when [radiation] is given early aren’t widely known yet," said Slawin.
Involvement of surgical margins of the prostatectomy specimen also appeared to be an important factor in the success of the salvage radiation. Men with positive margins were more likely to respond to radiotherapy, even if they also had high-grade disease. That’s because in such men, rising PSA levels are likely caused by residual cancer in the pelvis, Slawin and colleagues wrote; in men with negative surgical margins, rising PSA is more likely to be caused by metastatic disease.
Roach cautioned, though, that clear surgical margins alone shouldn’t be used to disqualify someone from salvage radiotherapy.
"Whether a margin is positive or negative can depend a lot on who’s looking at the margins," he said, suggesting that some pathologists may sample the prostatectomy specimen’s margins more completely than others. "I wouldn’t want people to reach the conclusion that if a patient doesn’t have positive margins, he won’t benefit from treatment."
Slawin said his findings suggest that a greater proportion of men who have a recurrence initially have localized disease. Based on the calculated four-year probability (45%), he estimated that 52% of patients with rising PSA levels after surgery fall into this category.
Yet most patients who receive secondary treatment after radical prostatectomy are given hormonal therapy, which is not curative, he wrote. Fewer than half receive salvage radiation.
"I think currently not enough men are being offered this therapy," Slawin said. "It seems that more men are good candidates."
The study could give physicians and patients a more reliable estimate of what to expect, based on clinical parameters, if they’re considering the treatment, he added.
Roach said the study also gives researchers a framework to design future trials in hopes of further improving outcomes for men in this situation.
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