Increased prostate cancer diagnoses tied to access to screening

USC study indicates jump in reported prostate cancers linked to availability of routine testing, not to changes in causes of cancer

LOS ANGELES, May 2, 2001—When cases of prostate cancer rose in the last two decades, more accessible testing and early detection most likely prompted the increase in incidence, conclude researchers at the Keck School of Medicine of the University of Southern California.

Soon after prostate-specific antigen (PSA) tests became available to detect prostate cancer in 1987, prostate cancer incidence increased steeply nationwide. Cases rose especially dramatically among men of high socioeconomic status—measured by income and education levels—compared to men of lower socioeconomic status, the researchers report in the May issue of the Journal of the National Cancer Institute. Before PSA testing became prevalent, doctors diagnosed fewer cases of prostate cancer, and cases were spread out almost equally among men of all socioeconomic groups (despite variations among ethnic groups). With their education and affluence, men of high socioeconomic status are more likely to benefit from improvements in disease detection, treatments and knowledge of risk factors. Easier access to health care increases the chances that these men—regardless of race or ethnicity—will be tested for prostate cancer, which naturally may result in a cancer diagnosis, says Lihua Liu, USC preventive medicine researcher and lead author of the study.

Using data from the Los Angeles Cancer Surveillance Program, preventive medicine researchers examined about 83,000 invasive prostate cancer cases reported in Los Angeles County from 1972 to 1997. They estimated each patient’s socioeconomic status based on income and education statistics for the Census tract in which the patient lived at time of diagnosis.

From 1972 to 1987, before PSA testing, researchers found no relationship between patients’ socioeconomic status and the prostate cancer incidence rate, regardless of race or ethnicity. Prostate cancer was diagnosed at about the same rate across all socioeconomic levels, within each racial or ethnic group. That changed after 1987. For men diagnosed in the 10 years after PSA testing started, the higher their socioeconomic status, the greater the incidence of prostate cancer. And, the higher a man’s socioeconomic status, on average, the earlier the stage of cancer found at diagnosis.

The USC study was the first to look at the connection between socioeconomic status and prostate cancer incidence while taking PSA testing into account. Results indicate that factors involved in socioeconomic status do not increase cancer risk.

However, Liu notes, other studies have shown that widespread use of PSA testing has resulted in the discovery of some non life-threatening tumors and latent prostate cancer (that is, an incidental lesion that, if left untreated, should not affect the duration or quality of a man’s life). Adds Liu: "The benefits of PSA testing and the potential for over-diagnosis and over-treatment need to be carefully evaluated."

Lihua Liu, Wendy Cozen, Leslie Bernstein, Ronald K. Ross and Dennis Deapen, The Changing Relationship between Socioeconomic Status and Prostate Cancer Incidence. Journal of the National Cancer Institute, Vol 93, No. 8, May 2, 2001.