Home > Newsroom > Publications> News Archive

Please note: This article is part of the Cancer Center's News Archive and is here for historical purposes. The information and links may no longer be up-to-date.

News Archive: Michigan Oncology Journal Spring 98

Recent Changes in Michigan’s Prostate Cancer Incidence: What Does It Mean?

-John T. Wei, M.D.,

-Robert Wood Johnson Clinical Scholar, American Foundation for Urologic Disease Scholar, and Lecturer in the Section of Urology, Department of Surgery

Rod Hayward, M.D.,
Director, Veteran Affairs Center for Outcomes Research, Ann Arbor, and Associate Professor, Department of Internal Medicine and School of Public Health

The Controversy
Prostate cancer remains among the most controversial health issues facing men today. An estimated 334,500 new cases will be diagnosed in the United States in 1997 with an associated mortality of 41,800 (1). The incidence of prostate cancer has slowly risen from 1965 to 1985, but beginning in the late 1980s, an epidemic of cases occurred (2). This has been attributed to the introduction of serum prostate specific antigen (PSA) as a diagnostic test for prostate cancer. The obvious explanation for this epidemic is that the use of PSA detects more cancers than digital rectal examination alone; (3, 4) however, other factors such as an increased public awareness leading to more diagnostic testing may also play a significant role. The medical community continues to debate the issue of screening for prostate cancer with PSA and whether it will lead to improved survival (5, 6).

Time Trends in Michigan
Since 1987, prostate cancer has been the leading site of cancer among men in the state of Michigan. These findings are especially pertinent to physicians in Michigan where the mortality rate from prostate cancer in African-American men is higher than Caucasians (7) and ranks among the highest in the world (8). In 1985, the Michigan Department of Community Health started a state-wide cancer registry of all cases of prostate cancer. This data has reflected national trends in the incidence of localized, regional and metastatic disease (figure 1). What can be clearly seen is an abrupt increase in the incidence of localized cases starting in 1990 and peaking in 1992. This is followed by an equally sharp drop in the incidence up to 1995. The incidence for regional disease also experienced a similar phenomena but to a lesser degree, and metastatic cases actually decreased by 51%. The explanation, of course, is that there has been a significant stage-shift for this disease from extra-prostatic to localized cases (figure 2). However, it should be noted that the incidence for both localized and extra-prostatic cases has not fallen below pre-PSA levels.

Clinical Relevance
What is the clinical relevance of these epidemiological data? Certainly, one view, albeit an optimistic view, is that the incidence of extra-prostatic disease in Michigan will continue to fall to levels below what it was in 1987 when PSA was introduced. This would appear to be intuitive since it has been shown that prostate cancer can be cured when localized (9), however, caution should be used in this interpretation. A significant drop in the incidence of extra-prostatic disease has not yet been demonstrated, and more importantly, the mortality rate has remained unchanged (figure 3). In order for a stage-shift to result in decreased mortality, curative treatment has to be given for cases of localized cancer that would ultimately lead to death. Simply reporting changes in survival for men with prostate cancer is misleading due to lead- and length-time bias (10). Lead-time bias is an apparent increase in survival due to earlier detection and without alteration of the natural history of the disease. Length-time bias is the “over-diagnosis” of less aggressive cases that would never have led to a prostate cancer death. To date, evidence of benefit from the use of PSA eludes us.

However, if extra-prostatic cancers continue to fall to levels below that observed in the pre-PSA era, this would provide preliminary evidence of benefit. Along with this, we would expect mortality rates to fall eventually, provided that curative treatment is being given to at-risk patients. PSA testing will soon be covered by Medicare at a tremendous cost to health care. It is incumbent on the medical profession to provide proof that the use of PSA test leads to lower mortality.

Current Investigation

How can we demonstrate a benefit from the use of PSA if the mortality rate remains unchanged? The gold standard technique is to perform a randomized control trial using PSA, but it will likely take a decade or more before such a study would yield results. Investigators at the University of Michigan Comprehensive Cancer Center hope to find early evidence of benefit by detecting a decrease in the proportion of extra-prostatic disease in men who undergo screening with PSA. Using a case-control study design, 500 men with extra-prostatic prostate cancer at the time of diagnosis will be identified and age-matched to 500 control men without extra-prostatic disease. An analysis of the screening rate (exposure) will reveal if there has been a significant drop in the proportion of extra-prostatic disease, which would lead to an improved survival benefit. Results from this study should be available within one to two years.

References

  1. Parker SL, Tong T, Bolden S, Wingo PA. Cancer statistics, 1997. Ca: a Cancer Journal for Clinicians. 47(1):5-27, 1997.
  2. Demers RY, Swanson GM, Weiss LK, Kau TY. Increasing incidence of cancer of the prostate. The experience of black and white men in the Detroit metropolitan area. Archives of Internal Medicine. 154:1211, 1994.
  3. Catalona WJ, Smith DS, Ratliff TL, Basler JW. Detection of organ-confined prostate cancer is increased through prostate-specific antigen-based screening. JAMA. 270:948, 1993.
  4. Jacobsen SJ, Katusic SK, Bergstralh EJ, Oesterling JE, Ohrt D, Klee GG, et al. Incidence of prostate cancer diagnosis in the eras before and after serum prostate-specific antigen testing. JAMA. 274:1445, 1995.
  5. Hall RR. Screening and early detection of prostate cancer will decrease morbidity and mortality from prostate cancer: the argument against. European Urology. 29 Suppl 2:24, 1996.
  6. Brawer MK. Screening and early detection of prostate cancer will decrease morbidity and mortality from prostate cancer: the argument for. European Urology. 29 Suppl 2:19, 1996.
  7. Pienta KJ, Demers R, Hoff M, Kau TY, Montie JE, Severson RK. Effect of age and race on the survival of men with prostate cancer in the Metropolitan Detroit tricounty area, 1973 to 1987. Urology. 45:93, 1995.
  8. Muir CS, Nectoux J, Staszewski J. The epidemiology of prostatic cancer. Geographical distribution and time-trends. Acta Oncologica. 30:133, 1991.
  9. Lepor H, Kimball AW, Walsh PC. Cause-specific actuarial survival analysis: a useful method for reporting survival data in men with clinically localized carcinoma of the prostate. Journal of Urology. 141:82, 1989.
  10. Russel L., Educated Guesses Making Policy about Medical Screening Tests. University of California Press; 1994.

 

Return to top


Small Text SizeMedium Text SizeLarge Text Size
Adjust text size

Speak with a Cancer nurse: 1-800-865-1125
make a donation
Please note: The articles listed in the Cancer Center's News Archive are here for historical purposes. The information and links may no longer be up-to-date.