The Future of Prostate Cancer Screening
Indeed, the studies – one from Europe, the other from the United States – found that during a seven- to nine-year follow-up, only small differences in mortality occurred between men who were tested and those who weren't. The authors raised the question of whether the PSA test exposes too many men to needless procedures that have potential side effects.
But David Jarrard, MD, a UW School of Medicine and Public Health professor of urology, says that the studies really underscore that the natural history of prostate cancer is quite long in most patients.
"Screening needs to be individualized, and not everyone will benefit from it," says Jarrard, who specializes in prostate cancer at the UW Carbone Cancer Center. "Screening is more likely to benefit younger individuals and those with over a 10- to 15-year expected lifespan. This is a discussion that men need to have with their doctors."
That's because older men with prostate cancer are likely to die of something else before the cancer becomes a problem. There is, however, a subset of men who have the more aggressive form of the disease that kills about 30,000 American men a year.
And, Jarrard notes, better tests are on the way that can augment the results of the standard PSA (prostate-specific antigen) screening test. Indeed, one of Jarrard's Wisconsin colleagues has discovered a promising connection between blood calcium levels and the more fatal type of prostate cancer.
"This is the key issue in prostate cancer: whom to treat and whom not to treat," says Halcyon Skinner, a faculty member in population health sciences. "Some prostate cancers are aggressive tigers, so we need a test that will separate the tigers from the pussycats."
Skinner recently co-authored a study, with Dr. Gary Schwartz of the Wake Forest University School of Medicine, that links high levels of ionized calcium in the blood to the fatal form of prostate cancer.
Skinner and Schwartz looked at test results from 6,700 men who had their blood drawn between 1988 and 1994 as part of the National Health and Nutrition Study. They found that men who had the highest levels of ionized calcium in their blood were three times more likely to later die of prostate cancer.
Skinner says that the results, a refinement of an earlier study, could quickly lead to a blood-calcium test that could give men and their physicians a stronger indication of when to treat the cancer, and when to watch and wait. Such a test could be most useful when deciding whether to do a biopsy of a suspected prostate tumor.
Jarrard agrees that such a test would be helpful, and said that other new tests, such as a blood test for early prostate cancer antigen-2 (EPCA-2) and a urine test for the DD3 genetic marker, are also coming.
"Clearly, we need better tests to allow us to predict the biology of these cancers," Jarrard says. "In the future, I think we're going to be using a panel of tests to help us decide who needs to consider therapy and who doesn't."
Date Published: 07/16/2009