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Public Health Briefings

Update: Prostate Cancer Screening

John P. Fulton, PhD, Joann M. Lindenmayer, DVM, MPH

Published in: Rhode Island Medicine, 1995;78(11) 330-331

John P. Fulton is Assistant Director, Division of Preventive Health Services, Rhode Island Department of Health, and Clinical Assistant Professor of Community Health, Brown University School of Medicine. Joann M. Lindenmayer, DVM, MPH is Assistant Professor, Research, of Community Health, Brown University School of Medicine.

Overview

The burden of prostate cancer in the U.S. is significant and appears to be increasing. Although prostate cancer is most likely to strike elders, men in their 40s and 50s may also be afflicted. Control of prostate cancer focuses on early detection, the subject of recommendations for case finding from the American Cancer Society (ACS), the National Cancer Institute (NCI), and the American Urological Association. However, clinical trials to determine the effectiveness of screening and treatment have not yet been completed, leaving key management issues unresolvable for the next decade.

Rising Incidence

Prostate cancer is common in the U.S. In 1994, an estimated 200,000 cases were diagnosed, up from an estimated 165,000 in the previous year.¹ Although most cases are diagnosed among white males, the age-standardized incidence of prostate cancer is higher among blacks than whites: 209.6/100,000 vs. 159.2/100,000 in 1991.² In comparison, the age-standardized incidence of breast cancer in the U.S. in 1991, was 95.1/100,000 and 113.6/100,000 for black and white females, respectively.²

The incidence of prostate cancer has risen steadily in the U.S. since 1973, when it was first measured by the NCI's Surveillance, Epidemiology, and End Results (SEER) program. Between 1973 and 1991, the incidence of prostate cancer among males of all races in the U.S. rose from 64.1/100,000 to 163.1/100,000. A full half of that increase occurred since 1989, when the incidence of prostate cancer for males of all races was determined to be 111.5/100,000.² The increase in incidence which occurred through 1986 is attributed largely to the identification of prostate cancer on pathology following transurethral resections of the prostate (TURPs) for obstruction or hypertrophy of the prostate.³ The sharp increase in prostate cancer incidence which occurred since 1986 is attributed largely to improved case finding "with the aid of digital rectal exam, transrectal ultrasound-guided needle biopsy, computed tomography, bone scan, and serum testing for prostate-specific antigen PSA."⁴

Significant Mortality

Prostate cancer causes substantial mortality in the U.S., accounting for an estimated 38,000 deaths in 1994.⁵ In tandem with incidence, the prostate cancer mortality rate is highest among men ages 65 and over, although it is not trivial among men ages 55-59 (14.1/100,000 in 1987-91) and 60-64 (37.7/100,000 in 1987-91).²

In sharp contrast to the rise in prostate cancer incidence in the U.S. since 1973, prostate cancer mortality has increased only slightly, from 21.7/100,000 among males of all races in 1973 to 26.8/100,000 among males of all races in 1991.² That mortality remained flat during an unprecedented increase in incidence supports the position that improved case finding contributed substantially to the latter.

Control Strategy

Too little is known of the causes of prostate cancer to prevent its occurrence. Thus the control of prostate cancer has focussed on early detection and treatment, with the goal of preventing metastasis. However, a number of unresolved issues complicate management decisions.

Unresolved Issues

In 1986, when the NCI published its Cancer Control Objectives for the Nation: 1985-2000, it classified screening for cancer of the prostate with the digital rectal examination under "Category 3: Screening Impact Uncertain," observing that "No randomized clinical trial with mortality as an end point has been conducted so that precise calculations of the impact of the examination [digital rectal examination, or DRE] on cancer mortality are not possible."⁶ Such data are still about 10 years away,⁷ preventing the adoption of population-based screening for prostate cancer at present. Nonetheless, in the same 1986 document the NCI asserted "The use of the digital rectal examination, however, is considered an essential part of good patient management. The early diagnosis of rectal and prostate cancers, in part through the appropriate use of rectal examinations in persons at high risk of one or both of the cancers, notably those over 50 years of age, could improve the outcomes for these patients."⁶ In short, absent the results of clinical trials in 1986, the NCI could not recommend mass screening with the DRE for prostate cancer, but advocated case finding with the DRE as an essential part of "good patient management." The most recent ACS recommendation (below) is consistent with the NCI rationale, promoting case finding, not mass screening, with the DRE and the serum PSA test. The addition of the serum PSA test fits the rationale, as it has been shown to improve case finding when used with the DRE.⁷

In a review of the recent literature, however, Slawin, Ohori, Dillioglugil, and Scardino argue that this is not the case: "Clear evidence exists that these two manifestations of prostate cancer [clinically significant and insignificant] can be distinguished by differences in established prognostic features, such as the volume, grade, and extent of tumor. Application of these criteria to the cancers detected by DRE, PSA, and TRUS [transrectal ultrasound] has clearly demonstrated that an overwhelming majority of cancers detected today are clinically significant tumors and are not part of the larger group of latent tumors present, which remain largely undetectable by these modalities. ... Widespread experience from various institutions consistently demonstrates that perhaps up to 10 to 15 percent of prostate cancers detected in PSA-based screening programs may be clinically insignificant, but that most tumors detected demonstrate features similar to prostate cancers detected by palpation. ... In three large screening trials for prostate cancer, in which almost 10,000 men older than 50 years were screened using various methodologies encompassing DRE, serum PSA levels, and TRUS, the cancer detection rate has remained about five to six percent for the initial year of screening and less than 10 percent through year three of longitudinal cohort studies, rates within the range expected if mostly clinical relevant cancers are being detected."⁷

If this were true without exception, arguments for the importance of early detection would be less compelling. Although a definitive resolution of this issue must await the results of clinical trials, researchers have attempted to use existing data to perform decision analyses of alternative treatments for clinically localized tumors. These analyses are being hotly debated in the literature and remain controversial. Nonetheless, at least one recent decision analysis of Medicare data⁸ has been found by others in the field "to be a sound, useful description of the clinical reality surrounding the treatment decision for localized prostate cancer."⁹ Its major findings were recently reviewed (September, 1995) by Albertsen at the International Conference on Prostate Cancer Screening, Early Detection, and Control, sponsored by the Centers for Disease Control and Prevention:

Resolving the Questions

Research on the benefits of early detection and aggressive treatment of prostate cancer is proceeding on two fronts. Long-term clinical trials should provide definitive information to inform screening and treatment decisions in about 10 years.⁷ Analysis of existing data with case-control designs and meta-analysis will help inform current decision-making, but given the limitations of these approaches, will remain controversial. A close attention to the literature is warranted, as relevant information is appearing at an accelerated pace.

Current Recommendations

The American Cancer Society recommends the DRE as part of a "regular annual physical checkup" for all men over the age of 40, with an annual serum PSA test to be added for men ages 50 and over and for men younger than age 50 who are African American or who have a significant family history of prostate cancer. The NCI recommends annual DRE, but does not recommend routine use of the serum PSA test. The American Urological Association, like the ACS, recommends annual use of the serum PSA test for men ages 50 and over and for men younger than age 50 who are at higher risk of developing prostate cancer. Neither the Canadian Task Force on the Periodic Health Examination nor the U.S. Preventive Services Task Force recommend for or against annual use of the DRE, and both recommend against routine use of the serum PSA test with asymptomatic men.¹⁰

References

1. Garfinkel L. Evaluating Cancer Statistics. CA - A Cancer J for Clinicians 1994;44(1):5-6.

2. Miller BA, Ries HAG, Hankey BF, Kosary CL, Harras A, Devesa SS, Edwards BK (eds). SEER Cancer Statistics Review: 1973-1991, National Cancer Institute. NIH Pub. No. 94-2789, 1994.

3. Potosky AL, Kessler L, Gridley G, Brown CC, Horm JW. Rise in prostatic cancer incidence associated with increased use of transurethral resection. J Natl Cancer Inst 1990;82:1624-1628.

4. Miller BA, Ries HAG, Hankey BF, Kosary CL, Harras A, Devesa SS, Edwards BK (eds). SEER Cancer Statistics Review: 1973-1990, National Cancer Institute. NIH Pub. No. 93-2789, 1993.

5. Boring CC, Squires TS, Tong T, Montgomery S. Cancer Statistics, 1994. CA - A Cancer J for Clinicians 1994;44(1):7-26.

6. Greenwald P, Sondik EJ. Cancer Control Objectives for the Nation: 1985-2000. NCI Monographs, Number 2. Bethesda, Maryland: National Cancer Institute, 1986.

7. Slawin KM, Ohori M, Dillioglugil O, Scardino PT. Screening for prostate cancer: an analysis of early experience. CA - A Cancer J for Clinicians 1995;45(3):134-147.

8. Fleming C, Wasson JH, Albertsen PC, et al. A decision analysis of alternative treatment strategies for clinically localized prostate cancer: Prostate Patient Outcomes Research Team. JAMA 1993;269:2650-2658.

9. Albertsen PC. Treatment intervention for clinically localized prostate cancer and outcome. In: Agenda of the International Conference on Prostate Cancer Screening, Early Detection, and Control, September 6-7, 1995. Centers for Disease Control and Prevention.

10. The U.S. Preventive Services Task Force. Screening for Prostate Cancer: Commentary on the Recommendations of the Canadian Task Force on the Periodic Health Examination. Am J Prev Med 1994;10(4):187-193.