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What's the Value?
- Categorized in: 2013 Compendium of Federal Medicine, Department of Veterans Affairs (VA), Oncology, Urology
Choosing the right model makes a significant difference. Etzioni and her colleagues reviewed published modeling studies of prostate cancer that extrapolated the ERSPC mortality reduction to the long-term U.S. settings, accounting for changes in primary treatment, rates of overdiagnosis, and contamination of the control arm of the PLCO trial by random screening. The group found that “screening plausibly explains 45%, and changes in primary treatment can explain 33% of the U.S. prostate cancer mortality decline,” according to their study published in Medical Care.4 Further, the models indicated that the absolute reduction in prostate cancer deaths as a result of screening is five times the originally reported rate.
Calibrating the model using the ERSPC, “[ensures] that screening would be found to save lives,” noted John Concato, MD, director of the Clinical Epidemiology Research Center at the VA Connecticut HealthCare System and medical professor of at Yale University in New Haven, Conn., in an editorial accompanying the Annals of Internal Medicine report. 5
Melnikow and colleagues further contend that the “projections from models are subject to mistaken assumptions and investigator biases and should not be accorded the same weight as evidence from randomized controlled trials. Melnikow and her colleagues served on the USPTF at the time the recommendation against screening was made.
The number of cancer cases that could be detected in a screened population is large; a single study in which men eligible for PSA screening had biopsy regardless of PSA level detected cancer in nearly 25% of men. The rate of overdiagnosis also depends on life expectancy at the time of diagnosis. A cancer diagnosis in men with shorter life expectancies because of chronic diseases or age is much more likely to be overdiagnosis. The precise magnitude of overdiagnosis associated with any screening and treatment program is difficult to determine, but estimates from the 2 largest trials suggest overdiagnosis rates of 17% to 50% for prostate cancer screening.
Benefits of Less Screening
The reference strategy used in the FHCRC model tests men annually from ages 50 to 74 and refers those with a PSA above 4 for biopsy. In the model, this strategy reduces the risk of prostate cancer to 2.15%, with a risk of overdiagnosis of 3.3%. Raising PSA thresholds for biopsy referral in older men maintains the reduction in death from prostate cancer (2.23%) while reducing overdiagnosis to 2.3%. Screening every other year and extending intervals for men with low PSA levels has little effect on the risk of death from cancer but reduces the number of tests by 59% and cuts false-positive results in half.
“Screening every year has a high cost for incremental benefit,” said Etzioni. “A more conservative threshold, perhaps as high as 10, for referral for biopsy of men in the 70s may be reasonable and will reduce treatment for disease that would likely remain asymptomatic. For men over 69 with PSA levels of 3 or less, I would stop screening. The chances that they will die of prostate cancer are nearly zero.”
“It’s important to keep prostate cancer in perspective. Less than 3% of men over age 70 will die from prostate cancer, while heart disease will kill 20% or more. On an individual basis, you would want to take general health status into account, as well as race, family history and previous PSA results,” Etzioni added.
The challenge in prostate cancer screening and treatment “lies primarily in the inability of PSA or other current technologies to distinguish the minority of aggressive prostate cancers from the much more numerous indolent prostate cancers that do not lead to cancer morbidity or mortality,” Kelley said.
Further complicating matters, the VHA’s recently published Prostate Cancer Intervention vs. Observational Trial (PIVOT) study showed no improvement in overall survival for men who have radical prostatectomy compared with those who did not, Kelley noted.
All the treatments for prostate cancer carry significant risk of serious quality-of-life impairment. Nearly 90% of American men with PSA-detected prostate cancer have early treatment with surgery, radiation or androgen deprivation therapy, according to the USPSTF recommendation. For every 1,000 men who have surgery, five will die within a month and 10 to 70 will have serious, nonfatal complications. At least 20% to 30% of men who receive radiotherapy will have urinary incontinence and erectile dysfunction. Some will have bowel dysfunction. Androgen deprivation therapy causes erectile dysfunction in 40% of treated men.
Kelley, Concato and Etzioni agree that the current debate about the value of testing and increasing awareness of the harms of treatment makes patient involvement in decisions more important than ever. “There is an important role for patients to decide if the known burden of treatment is worth the uncertain benefits. Some patients may feel strongly that it is worth it for them,” Etzioni said.
The VHA has proposed a team-based model of oncology care that would ensure patients receive complete, accurate and unbiased information about the harms and possible benefits of prostate cancer treatment options through multiple channels and can discuss their options with a primary care provider, Kelley pointed out.
That’s a move in the right direction, according to Concato. “Uncertainty still reigns about the effectiveness of screening for prostate cancer. Therefore, patients should have considerable input into what happens, using shared decision-making, an activity that is easier said than done,” he noted.
1 Gulati R, Gore JL, Etzioni R. Comparative effectiveness of alternative prostate-specific antigen-based prostate cancer screening strategies. Ann Intern Med. 2013; 158(3):145-153.
2 Melnikow J, Lefevre M, Wilt TJ, Moyer VA. Counterpoint: Randomized trials provide the strongest evidence for clinical guidelines: The US Preventive Services Task Force and prostate cancer screening. Med Care. 2013:51(4)301-303.
3 Moyer VA. Screening for prostate cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2012;157:120-134.
4 Etzioni R, Gulati R, Cooperberg MR, Penson DM, Weiss NS, Thompson IM. Limitations of basing screening policies on screening trials: The U.S. Preventive Services Task Force and prostate cancer screening. Med Care. 2013;51(4):295-300.
5 Concato J. Probability, uncertainty, and prostate cancer. Ann Intern Med. 2013;158(3):211-12.
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