Prostate Cancer Screening Affected By Lifestyle and Demographics
Factors related to lifestyle and demographics may actually affect the reliability of prostate cancer screening according to research by Seattle-based Fred Hutchinson Cancer Research Center.
The study, appearing in the online version of the journal Cancer, shows that changes in concentration of prostrate specific antigen (PSA) otherwise known as PSA velocity is affected by factors like race, age or diet. Such PSA levels could easily be misinterpreted as signs of cancer.
Reviewing data on PSA and PSA velocity pertaining to 3,341 cancer-free menthe researchers found a relationship between PSA test results and specific lifestyle or demographic factors. Despite age and body mass index (BMI) being statistically significant, they had little influence in the interpretation of PSA test results.
The study found that PSA velocity decreased with aging in men and increased as their diets became richer with high calorie foods. Also PSA velocity in blacks was found to be twice as that of whites on an average and those who used high-dose calcium supplements had lower PSA values. Men who gained weight also enjoyed PSA results while those who lost weight had higher PSA results. These factors seemed to work in a manner to affect the end values of the test, making clinical interpretation of PSA velocity difficult if not biased.
Dr. Alan Kristal, lead scientist in the study opined that reliance on the PSA velocity tests could cause unnecessary biopsies besides trauma for many. Kristal said, “This is not going to be the solution. It’s not going to save the whole screening process from the problems of PSA”. The PSA velocity test was developed in an effort to improve the reliability of the commonly used PSA test that is known to have its drawbacks.
The most lethal cancer in men, prostate cancer has over 232000 new cases reported every year in the United States alone, one percent of whom will die as a result. Experts believe that annual prostate-cancer screenings from the age of 50 may help reduce the fatalities by early detection and treatment. The current methods of screening available include a rectal exam besides a PSA test that identifies from the concentration of antigen in the bloodstream.
However, several studies have questioned the reliability of PSA. One recent study done by “The Hutch” in 2004 showed that nearly 3 out of 20 men between 62 and 91 years with normal PSA tests were later diagnosed with prostate cancer. At that point in time some physicians believed that PSA velocity tests provided better reliability. Give that PSA values were affected by aging they believed that PSA readings over time could point out to increases that were abnormal. The new study by Kristal and his team now points to there being multiple factors that affect the PSA velocity and the difficulty in interpreting which factor affected the test results.
This difficulty in interpreting PSA tests is exactly what 63-year old Melvyn Raider has experienced. Raider thought that doing the tests could catch a cancer early and began doing them in his 50s. Raider with three abnormal tests in five years underwent biopsies three times as a result extracting four, eight and finally 14 samples. Raider who teaches at Wayne State University said, “There’s probably not much prostate left after all those samples”. With the biopsies yielding negative results for malignancy Raider says, “I’m out of the woods for a while. But if this same pattern continues, I’ll be back where I started”.