Obesity reduces reliability of PSA test

As weight goes up, PSA goes down. That is the conclusion of research to be published in March in Cancer, the journal of the American Cancer Society. Researchers say this makes any prostate screening antigen test likely to produce unreliable results in this population.

Obesity already appears to increase the risk of fatal prostate cancer. A American Cancer Society study in April 2003 added prostate cancer to the list of cancers linked to an unhealthy body weight, with men at the highest BMI at 34% higher risk. Studies also show obesity is associated with poor prognosis as well. Obese men with prostate cancer are diagnosed at more advanced stages and have higher mortality rates.

This led to the hypothesis that obesity may actually make available screening tests insensitive which this research was designed to test. Jacques Baillargeon of the University of Texas Health Science Center in San Antonio and colleagues investigated the association between BMI and PSA levels in 2779 men without prostate cancer in a study sponsored by the Early Detection Research Network of the National Cancer Institute.

The researchers found that as BMI increased, PSA linearly decreased. This finding was consistent regardless of age and race.

These findings, the authors conclude, may explain 'the recent reports of inferior outcomes of prostate cancer treatment in obese men' in that they 'may be caused by delayed detection' rather than biological differences in the tumor. The study implies that physicians may consider adjusting PSA values when screening for prostate cancer if men are overweight or obese.