| Prostate-specific antigen level five years after radiation predicts disease-free survival The blood level of prostate-specific antigen present five years after radiation treatment can help predict the patient's disease-free survival for the next several years, according to an article in the October 2002 issue of the International Journal of Radiation Oncology, Biology and Physics. Researchers have discovered that patients who maintain very low five-year prostate-specific antigen levels have a very low probability of relapse at 10 years and beyond. The study identified 328 men with prostate cancer treated with external beam radiation who were biochemically disease-free five years after treatment per American Society of Therapeutic Radiation Oncology criteria. The median follow-up period was 7.4 years. The patients were divided into four groups according to their antigen level five years after treatment: level less than or equal to 0.5, level of 0.5 to 1.0, level of 1.0 to 2.0, and level of 2.0 to 4.0 ng/mL. Prostate-specific antigen progression-free rates were calculated in each subgroup at 10 years after treatment. The prostate-specific antigen progression-free survival rate was 87 percent, 79 percent and 67 percent, respectively, at 8, 10, and 13 years after treatment in patients who were biochemically free of disease five years after treatment. The progression-free rates at 10 years after treatment according to five-year antigen level were 92 percent for a level less than or equal to 0.5 ng/mL, 71 percent for level 0.5 to 1.0 ng/mL, 78 percent for level 1.0 to 2.0 ng/mL and 56 percent for level 2.0 to 4.0 ng/mL. The lower the prostate-specific antigen level at five years, the more durable the probability of maintained biochemical disease-free survival. Researchers concluded that when prostate-specific antigen levels remain low (less than 2 ng/mL) five years after external beam radiation therapy, the great majority of patients will be biochemically disease free at 10 years. The hazard rates of biochemical progression in the 6 to 10 years after treatment are low and are comparable to rates seen when prostatectomy is the chosen treatment modality. "This study reinforces the fact that
radiation therapy should be used to achieve low prostate-specific
antigen levels early in treatment, and those low levels should be
maintained to five years and beyond," said Anthony L. Zietman,
M.D., study coauthor. "If this can be achieved, the long-term
outlook for prostate cancer patients treated with radiation therapy
will be good." |