TUESDAY, May 29, 2007 (HealthDay News) -- A rapid rise in blood levels of prostate specific antigen (PSA) over the course of a year -- a diagnostic indicator known as "PSA velocity"-- is the single most important marker for a particularly aggressive and deadly form of prostate cancer, new research suggests.
Reporting in the July 1 issue of Cancer, the authors say that an increase by two points or more of PSA over one year is a better predictor of death from prostate cancer than either a one-time "snapshot" of PSA levels at diagnosis, or a doctor's assessment of the stage of cancer prior to treatment.
"We know that, without any other factors, PSA velocity is a very good predictor of prognosis," said study leady author Dr. Anthony V. D'Amico, the chair of genitourinary radiation oncology at Brigham and Women's Hospital and professor of radiation oncology at Harvard Medical School in Boston. "It all depends on where it's been and where it's going," he said.
The American Cancer Society notes that, outside of skin cancer, prostate cancer is the most common form of cancer diagnosed among American men. This year nearly 220,000 new cases of the disease are expected to be diagnosed, and about 27,000 men will die of the disease.
The organization currently recommends that men at high risk for prostate cancer, which includes blacks and men with a family or personal history of the disease, should begin undergoing yearly digital rectal exams and PSA blood tests between the ages of 40 and 45.
Otherwise, men with average risk should begin screening at age 50, the society suggests.
D'Amico and his colleagues analyzed data on almost 950 men between the ages of 62 and 76 who underwent either surgical or radiation treatment for prostate cancer at one of four hospitals between 1988 and 2004.
At the time of diagnosis, all the patients displayed at least one indicator of aggressive prostate cancer: either a high absolute PSA reading; poor biopsy results regarding the health of prostate tissue at the cellular level; an advanced stage tumor; or a notable jump in their PSA velocity in the year prior to treatment.
Almost 70 percent of the patients had one of these high-risk markers at diagnosis, the researchers noted. A PSA velocity "bump" was the sole high-risk indicator of 44 percent of the men who went on to require surgery, and among 28 percent of those who underwent radiation therapy.
The researchers also tracked the men's post-treatment outcomes. They found that, for those who'd undergone surgery, 29 ultimately died from prostate cancer by 2006. Of those who received radiation, 32 went on to die from the disease.
Patients who had been diagnosed with more than one high-risk factor were at a significantly higher risk for dying from prostate cancer than were men diagnosed with just a single indicator of aggressive disease.
But a PSA velocity jump of 2.0 points or more in the year before treatment was the best single predictor of a poor outcome overall, the researchers said. This observation held true regardless of whether a patient had surgery or radiation.
In fact, a rapid PSA velocity was the sole prognostic indicator for 80 percent to 88 percent of the men with just one predictive marker who died from prostate cancer.
The take-home message from the study: A bump in PSA velocity of two or more points in the year prior to diagnosis and treatment is a strong enough indicator, on its own, of a particularly aggressive cancer requiring aggressive treatment. That treatment may involve the use of more than one therapy at a time, the researchers said.
"I'd say now that the issue regarding PSA velocity is nailed down, because it's clear that if your velocity rises in the short term, it's bad news," said D'Amico.
He stressed that more long-term research is needed to track patients beyond the study's seven-year timeframe, to assess the usefulness of PSA velocity in predicting outcomes even further down the road.
"But already what's clear from this study," added D'Amico, "is that if a man presents with what is believed to be a non-aggressive cancer but his PSA has risen rapidly in the year prior to diagnosis -- more than 2 points-- then that single fact alone means that treatment with more than just surgery or radiation is needed to maximize cure."
Another expert stressed that treatment decisions can still be tough, however.
Dr. Nelson Neal Stone is clinical professor of urology and radiation oncology at the Mount Sinai School of Medicine in New York City. He said the jury is still out with respect to which therapies deliver the best benefit to individual patients with rising PSAs.
"We do know from several studies that it is a bad sign for patients to have a rapidly rising PSA before they begin treatment," he said. "But that does not mean we know the solution. It's just not that clear, quite frankly. There's a suggestion that patients with a fast-rising PSA should be treated with combination therapies. But it's not proven that this is the way to go."
Stone does encourage patients to get an early handle on their PSA velocity trends by establishing a clear baseline record, however.
"Get three or so tests in the first year of screening, so you know where you're going from there," he said. "No matter what the treatment will be, it's certainly better to catch a rising PSA when it's going from 1.5 to 5.0, rather than 5 to 12. Then the patient is a lot more curable -- when you catch the rise early."
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