They are no more likely to die in the next 10 years than patients whose levels do not go up and down, according to the study.
Also, the study found, the prostate cancer is no more likely to return in men who have the rise in prostate specific antigen (PSA) — the so-called "PSA bounce" — than in those who do not, says researcher Eric Horwitz, M.D., clinical director of the radiation oncology department at Fox Chase Cancer Center in Philadelphia.
Horwitz's study looked at more than 7,500 prostate cancer patients treated with radiation.
Increased levels of PSA, a protein produced by the prostate, may be a sign of prostate cancer. But in men who have radiation treatment for prostate cancer, a temporary rise and fall in PSA levels is common. It affects up to half of patients, Horwitz says.
Horwitz tells WebMD the new findings are "a huge deal" for both doctors and men with prostate cancer. Patients typically become extremely anxious and may even have unnecessary chemotherapy or hormone treatment if they have a temporary rise in PSA.
Robert J. Cole, M.D., a prostate cancer specialist at the Cancer Center in Morristown, N.J., who was not involved with the study, agrees.
"This is another nail in the coffin for the PSA bounce," he says. "We can point to this landmark study and tell patients that 7,532 men were examined and the PSA bounce did not have any impact on the curability or the success rate of the treatment. That's pretty impressive."
Horwitz's study was presented at the American Society for Therapeutic Radiology and Oncology's annual meeting being held in Philadelphia.
The researchers studied men who were treated with either external beam radiation therapy or radiation seed implants. In external beam radiation therapy, a beam of high-dose radiation is aimed at the prostate to kill cancer cells. In radiation seed implant therapy, or brachytherapy, surgeons implant tiny radioactive seeds into the prostate gland. The seeds deliver high-dose radiation directly to the prostate for a predetermined length of time.
Over the 10 years following treatment, 902 of the men in the study who were treated with external beam radiation therapy and 470 of the men given seed implants experienced a PSA bounce.
But the study showed no significant difference in success rates among patients who had a bounce and those who did not. Among its findings:
The chance of cancer spreading elsewhere was also similar in both groups.
Horwitz says the reason men with the seed implants fared better is they tended to have earlier-stage cancer.
No one knows for sure why men treated with radiation experience a temporary rise and fall in PSA levels, but Cole says most doctors believe it's associated with the death of cancer cells.
"It's like when you throw water on a fire," he tells WebMD. "At times there may be a whole lot of smoke and you think the fire is getting worse. But eventually it calms down and the fire is out."
So what should you do if have a rise in your PSA level after radiation?
"You have to get a few readings over the next year," Horwitz says, adding that most doctors recommend screening every three months or so. "But try to relax and realize that it's OK, that this happens, and that a bounce does not mean your cancer has recurred."
SOURCES: American Society for Therapeutic Radiology and Oncology's annual meeting, Philadelphia, Nov. 5-9, 2006. Eric Horwitz, M.D., clinical director, radiation oncology department, Fox Chase Cancer Center, Philadelphia. Robert J. Cole, M.D., Cancer Center, Morristown, N.J.
By Charlene Laino
Reviewed by Louise Chang, M.D