Two Studies Aid Understanding of Prostate Cancer

New Studies Aid Understanding of Prostate Cancer

For men with prostate cancer, a rise in prostate-specific antigen (PSA) levels after radiation therapy - called PSA bounce - is not clinically relevant and does not affect survival, say researchers at a recent American Society for Therapeutic Radiology and Oncology meeting.

In addition, a second study shows that a rapidly rising PSA level before treatment is a sign that the cancer has most likely spread beyond the prostate and that hormone therapy, in addition to radiation, is called for.

PSA is a protein produced by the prostate gland. A PSA test measures levels of PSA in the blood. It is normal for men to have low blood levels of PSA, but prostate cancer can increase PSA levels.

Survival Not Affected by PSA Bounce

In the first study, researchers led by Dr. Eric Horwitz, clinical director of Fox Chase's Radiation Oncology Department, sought to determine whether there was a difference in survival between men who had a PSA bounce after radiation therapy compared with men who did not.

The researchers collected data on more than 7,500 men treated either with external-beam radiation or with radioactive seed implants.

They found that a significant number of men had at least one PSA bounce within one to three years after treatment. However, there were no differences in survival of patients who had a bounce and those who did not.

"PSA bounce, which happens in 50 percent of men who get treated with radiation, doesn't have any clinical significance," says Dr. Horwitz. "It does not mean that your cancer comes back.”

Dr. Horwitz notes that, in the past, a PSA bounce was thought to mean that the cancer had returned and the patient needed hormone treatment.

"Hormone treatment has many side effects," he said. "If the cancer has not returned, you certainly don't want to have additional treatment.”

Dr. Durado Brooks, director of prostate and colorectal cancers at the American Cancer Society, thinks this study should help reassure men that PSA bounce does not mean their cancer has returned.

"It appears that PSA bounce after radiation is insignificant," notes Dr. Brooks. "This transient increase doesn't seem to make any difference in long-term survival. This should be reassuring to men."

PSAV Test Can Determine Cancer Spread

In the second study, Dr. Mark K. Buyyounouski at Fox Chase collected data on 671 men with clinically localized prostate cancer who received 3-D conformal radiation therapy between 1989 and 1999.

Dr. Buyyounouski found that the rate of rise in PSA levels, known as PSA velocity (PSAV), can determine when prostate cancer may have already spread, even in men with clinically localized disease.

"Men whose PSA is rising rapidly prior to treatment appear to be at higher risk for having disease outside of the prostate," says Dr. Buyyounouski. "This has been shown to be a risk factor for death from prostate cancer."

His team found that when PSAV was greater than 2 nanograms per milliliter per year, PSA was likely to continue rising at the same rate despite radiation therapy.

In addition, men with a rapidly rising PSAV were more likely to have a cancer spread beyond the prostate and a greater risk of dying from the disease. But, this relationship was not seen for men with a PSAV of less than 2 nanograms per milliliter per year.

"These men with a rapidly rising PSA need treatment to more than the prostate area," explains Dr. Buyyounouski. "They should strongly consider hormone therapy, which is the standard of care for men with a high risk of distant spread of cancer."

Hormone therapy has been shown to improve survival for men at high risk of undetected spread of prostate cancer, he adds.

Dr. Brooks says, “This study is in line with a lot of other work that has been done in PSAV. There is a growing body of evidence that supports the fact that a rapid rise in PSA is associated with more severe disease and possibly with worse long-term outcome."

Always consult your physician for more information.