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Studies focus on diagnostic testing and treatment for prostate cancer

Prostate cancer is the most commonly diagnosed non-skin cancer in men and the second leading cause of cancer death, with nearly 180,000 new cases and 37,000 deaths in 1999. Unfortunately, much controversy still surrounds the screening, diagnosis, and treatment of prostate cancer.

A recent study supported by the Agency for Healthcare Research and Quality (HS06992) finds that an American Cancer Society guideline supporting the annual screening of men aged 50 and older for prostate-specific antigen (PSA, a marker of prostate cancer) may have fueled an increase in this testing from 1992 to 1994 in one State. A second AHRQ-supported study (Evidence-based Practice Center contract 290-97-0015) demonstrates that survival chances for men with advanced prostate cancer are about the same whether they have their testes removed or receive one of the common medications for this cancer. The two studies are summarized here.

Moran, W.P., Cohen, S.J., Preisser, J.S., and others. (2000, March). "Factors influencing use of the prostate-specific antigen screening test in primary care." American Journal of Managed Care 6(3), pp. 315-324.

Physicians who believe in aggressive screening for prostate cancer support routine PSA screening (a simple blood test) of all men beginning at age 50 years, screening of high-risk patients at younger ages, and surgery for diagnosed disease. Proponents of conservative strategies oppose all prostate cancer screening and espouse "watchful waiting" with treatment of symptoms for diagnosed cases. Controversy continues without definitive evidence.

In late 1992, the American Cancer Society (ACS) approved a clinical practice guideline recommending that all men aged 50 and older have annual PSA screening for prostate cancer. These researchers found that more than 400 primary care physicians in Colorado increased the odds of PSA testing of men aged 50 years and older by more than three-fold between 1992 and 1994. Their PSA screening increased from 24 percent of men in this age group in 1992 to 35 percent in 1993 and 40 percent in 1994.

Of the surveyed physicians, 89 percent rated the ACS as moderately or highly influential on their cancer screening practices. Fewer than one-third of the surveyed physicians reported being moderately or strongly influenced by the U.S. Preventive Services Task Force, which has recommended against the use of PSA and other prostate cancer screening interventions.

Thus, the authors attribute at least part of the increase in PSA testing by these Colorado physicians to release of the ACS clinical practice guideline. Physicians' use of the digital rectal exam (DRE) to screen for prostate cancer did not significantly change over the 3-year study period (39 percent in 1992 to 36 percent in 1994).

Seidenfeld, J., Samson, D.J., Hasselblad, V., and others. (2000, April). "Single-androgen suppression in men with advanced prostate cancer: A systematic review and meta-analysis." Annals of Internal Medicine 132(7), pp. 566-577.

The chief goal of therapy for advanced prostate cancer is to eliminate the male hormone androgen, which speeds progression of the disease and its symptoms. Several methods are used to decrease androgen levels for these men, ranging from removal of both testes (orchiectomy) to androgen-blocking agents such as luteinizing hormone-releasing hormone (LHRH) agonists and nonsteroidal antiandrogens. A meta-analysis of 24 randomized, controlled trials involving more than 6,600 men concludes that the available monotherapies for metastatic prostate cancer are largely interchangeable, including testes removal and medications.

Analysis revealed that survival after therapy with an LHRH agonist was equivalent to survival following orchiectomy or treatment with diethylstilbestrol (DES), the earliest methods for treating advanced prostate cancer. Ten trials involving 1,908 patients reported overall survival at 2 years, 5 years, or median survival, with no significant difference among orchiectomy, LHRH agonists, and DES (an intermediate dose). No trials showed a difference in effectiveness among the LHRH agonists, such as leuprolide, goserelin, and buserelin, even though these medications differ substantially in cost.

Although DES may be a good alternative to LHRH agonists and is much less expensive, it is currently unavailable commercially in the United States because it is known to be cardiotoxic at high doses.

Men treated with nonsteroidal antiandrogens (for example, flutamide, nilutamide, and bicalutamide) and steroidal antiandrogens seemed to have lower survival rates, and no trials favored nonsteroidal antiandrogen monotherapy. Treatment withdrawals, the most reliable indicator of adverse effects, occurred less with LHRH agonists (0-4 percent) than with nonsteroidal anti-androgens (4-10 percent). Although patients prefer to avoid orchiectomy, there was insufficient evidence to conclude whether the procedure actually decreased quality of life compared with other monotherapies.

This research was conducted by the Blue Cross and Blue Shield Association Technology Evaluation Center in Chicago, IL, an AHRQ-supported Evidence-based Practice Center.

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