WEDNESDAY, July 7, 2004 (HealthDayNews) -- Men with prostate cancer whose PSA levels increased significantly the year before diagnosis and surgery had more aggressive forms of the disease and were more likely to die within seven years.
That's the finding of a new study that concludes that PSA (prostate-specific antigen) testing results should be tailored to the health profile of each man.
"This study shows fairly conclusively that it is not the absolute number but how it changes over time," said Dr. Anthony D'Amico, lead author of the study appearing in the July 8 issue of the New England Journal of Medicine.
"Just like with mammograms, you don't look at a single snapshot in time, you look at the continuous spectrum. The PSA velocity [how it changes over time] is the most important predictor," he said.
D'Amico is radiation oncologist at Brigham and Women's Hospital, Harvard Medical School and Dana Farber Cancer Institute, all in Boston.
Interestingly, half of the men who had the greater PSA velocity in this study were classified, by conventional means, as low-risk patients.
The study authors suggest men get a baseline PSA test at age 35, then additional PSA tests once a year thereafter.
Prostate cancer is the second most common cancer in American men. Despite substantial advances in recent years, some 82 men in the United States still die of the disease every day, according to an accompanying editorial in the journal.
PSA is a protein produced by the cells of the prostate gland. The prostate-specific antigen test measures the level of PSA in the blood. When the prostate enlarges, PSA levels typically rise. The levels can rise due to cancer or benign conditions, according to the National Cancer Institute.
While PSA testing has become commonplace, physicians have been unclear how to interpret the results. In particular, they have been wrestling with what absolute number might predict the presence of cancer, D'Amico said.
The new study analyzed PSA data from 1,095 men, all approximately 65 years old, who had undergone a radical prostatectomy within about a month of their diagnoses. PSA levels were measured every six to 12 months both before and after surgery.
Men whose PSA levels increased by more than 2 nanograms per milliliter of blood during the year before being diagnosed had a higher risk of dying from prostate cancer within seven years, even if they underwent a radical prostatectomy. "There was a tenfold increased risk of death from prostate cancer if you went up by two points in a year" prior to diagnosis, D'Amico said.
Surgery or local radiation may not be enough for men whose PSA levels are in the fast-rising group, D'Amico added. "They could have surgery but then expect to follow that with radiation and hormonal treatments," he added. Certainly "watchful waiting" would not be a good option.
What the study doesn't reveal is how to treat a man whose PSA levels rose less than two points in a year.
"Significant rises of more than two are ominous. Rises of less than that are still amenable to cure with local therapy [but] we don't know the lower threshold," D'Amico said.
Still, said Dr. Mark H. Kawachi, director of the Prostate Cancer Center at City of Hope Cancer Center in Duarte, Calif., the study does "help us refine the way we look at prostate cancer patients."
"Individualized treatment becomes the issue here," Kawachi said. "The exciting thing about this study is it comes at a time when chemotherapy for advanced prostate cancer is demonstrating bona fide benefit. So we do have options now, whereas two to three years ago we wouldn't have had very many options to even consider."
For more on the PSA test, visit the National Cancer Institute.