October 9, 2008 — For the first time, the US Preventive Services Task Force (USPSTF) recommends that routine colorectal cancer (CRC) screenings can eventually be stopped in individuals older than 75 years who have a consistent history of negative screening results and in all adults older than 85 years.
These and other new recommendations from the task force appear in the October 6 Online First issue of the Annals of Internal Medicine and will be in the November 4 print edition of the journal.
The recommendation to stop screening is "bold," commented observer Francis M. Giardiello, MD, John G. Rangos, Sr, professor of medicine at the Johns Hopkins University School of Medicine in Baltimore, Maryland. "I have sat on these [recommendation] committees in the past and no one ever wanted to set a stop age."
Also, the USPSTF now recommends that adults aged 50 to 75 years be screened with either annual high-sensitivity fecal occult blood testing or sigmoidoscopy every 5 years, with high-sensitivity fecal occult blood testing between sigmoidoscopic examinations or colonoscopy every 10 years.
"Life years saved is just about the same for the 3 different approaches to screening. You can choose from these 3," said Ann Graham Zauber, PhD, associate attending biostatistician in the Department of Epidemiology and Biostatistics at Memorial Sloan-Kettering Cancer Center in New York City, in an interview with Medscape Oncology. Dr. Zauber was the lead author of a decision analysis that was commissioned by the task force and helped compare different cancer screening strategies as well as determine the age to stop and start screening. The analysis, along with a systematic evidence review, was used to update the USPSTF's recommendations, which were last issued in 2002.
Computed Tomographic Colonography and Fecal DNA Testing Have Insufficient Evidence
In its recommendations, the USPSTF concludes that the current evidence is "insufficient to assess the benefits and harms" of computed tomographic (CT) colonography and fecal DNA testing as screening modalities.
Clinicians should know why the task force is not recommending CT colonography at this time, said Evelyn P. Whitlock, MD, MPH, director of evidence-based medicine at the Kaiser Permanente Center for Health Research in Portland, Oregon, in an interview with Medscape Oncology. "When you screen, the first consideration is 'Do no harm.' There are uncertainties about radiation risk and CTC [CT colonography], especially with regard to repeat screenings over time. Also, because CTC is imaging more than the colon, up to 16% — which is a conservative figure — of patients will need additional testing for follow-up of incidental findings outside the colon. It's not clear what the implications of these extra-colonic findings are," she said.
Also, somewhere between 1 in 3 to 1 in 8 patients who undergo CT colonography will need additional colonoscopy after a scan because CT colonography is a screening tool and is not used diagnostically or therapeutically, she said. Dr. Whitlock was the lead author of the systematic evidence review commissioned by the USPSTF; this review is also available online.
In addition, it is "not clear" what the performance of CT colonography will be in detecting adenomas and cancer in the community setting vs research centers, she said.
In discussing the new recommendations, Dr. Whitlock emphasized that neither fecal DNA testing nor older, less sensitive occult blood tests such as the Hemoccult II (Beckman Coulter Primary Care Diagnostics, Fullerton, California) are included in the recommendations to use fecal occult blood testing (either annually or in the years between 5-year sigmoidoscopy examinations). "Clinicians should be aware that the FOBT [fecal occult blood test] recommendations are for the new high-sensitivity tests — either high-sensitivity guaiac testing or the fecal immunochemical tests," she said.
To qualify as a high-sensitivity fecal occult blood test, a technology has to have a sensitivity for cancer of 70% or more and a false-positive rate of less than 10% (ie, specificity > 90%), according to the task force statement.
USPSTF vs ACS-MSTF
The new recommendations from the USPSTF contrast with recommendations earlier this year from the American Cancer Society–US Multi-Society Task Force (ACS-MSTF), which were commissioned by the American Cancer Society and issued jointly by professional societies representing gastroenterology and radiology. It is notable that the ACS-MSTF recommended both CT colonography and fecal DNA testing, whereas the USPSTF did not.
An editorial that accompanies the new guidelines from the USPSTF provides commentary on the different recommendations and processes of the 2 bodies. "The ACS-MSTF panel did not use decision modeling or a systematic review to reach its recommendations, nor did it grade the strength of the evidence or formally rate the strength of each recommendation [the USPSTF did all of the above]. It did identify recommendations that it based solely on clinical judgment," write Michael Pignone, MD, MPH, associate professor of medicine at the University of North Carolina-Chapel Hill, and Harold C. Sox, MD, editor of the Annals of Internal Medicine.
"In short, we think the public is best served by a relatively structured, comprehensive, transparent approach in which the entire body of evidence drives the recommendations," they conclude, thus endorsing the USPSTF's approach to CRC screening recommendations.
Stop Screening After Age 75 Years
Dr. Zauber emphasized that the recommendation to stop routine screening after age 75 years is based on a patient not having any adenomas or CRC during 25 years of past screenings. Individual patients older than 75 years may have a need for screening, she reminded. However, for people without a history of lesions, "continued screening beyond 75 does not add life years for an individual," she said.
"There is a substantial lead time between the detection and treatment of colorectal neoplasia and a mortality benefit, and competing causes of mortality make it progressively less likely that this benefit will be realized with advancing age," the task force comments in its recommendations.
Start Screening at Age 50 Years; What About Young People With Polyps?
"There is convincing evidence that screening with any of the 3 recommended tests [high-sensitivity fecal occult blood testing, sigmoidoscopy, and colonoscopy] reduces colorectal cancer mortality in adults age 50 to 75 years," according to the task force statement.
Dr. Zauber noted that the point of the recommendations is to choose a test that a patient will agree to and then keep to the intervals, including the start at age 50 years.
Dr. Whitlock agreed that it is important to find ways to have people both start and keep to the recommended screening. "We are woefully behind in the getting the general population screened," she said.
With regard to the recommended start age of CRC screening, a new study by Pendergrass and colleagues shows that the prevalence of colorectal adenomas "sharply increases" after age 50 years. This study, based on 3558 persons in whom autopsies were performed from 1985 to 2004 at Johns Hopkins Hospital, appears in the September 2008 issue of Clinical Gastroenterology and Hepatology. However, although the study is a reconfirmation of the appropriateness of starting screening at age 50 years, that was not the goal of the study, noted Dr. Giardiello, a coauthor.
"How many polyps are normal in young people? That's the question I pursued in this study," Dr. Giardiello told Medscape Oncology. "This is relevant to me when I see a 40-year-old with three adenomas and wonder how normal or abnormal that is."
The individuals in whom autopsies were performed at Johns Hopkins ranged in age from 20 to 89 years and provided Dr. Giardello and colleagues with a strong sample of both younger patients (n = 1001 from ages 20 - 49 years).
"In younger adults, the prevalence of adenomas increased steadily from 1.72 to 3.59 per hundred autopsies from the third to the fifth decade of life. This rate sharply increased after 50 years of age with the prevalence of adenomas ranging from 10.1 to 12.06 per hundred autopsies in the sixth and ninth decade of life, respectively," write the authors. There was no limitation with regard to the size of the adenomas detected at autopsy in the study.
The study by Pendergrass and colleagues reveals that adenomas in people younger than 50 years are rare. It also indicates that the mean number of adenomas occurring in affected younger adults ranges from 1.0 to 1.1. "So, if you see someone in the clinic under age 50 with 2 polyps, that is 2 standard deviations from the mean and indicates that the patient needs to be looked after closely," said Dr. Giardiello.
This study also found that, for persons older than 50 years, the mean number of adenomas was 5; any number of adenomas above that number should be considered outside the "normal expectation," he said.
The study also reveals that blacks in both age groups (≤ 49 years and ≥ 50 years) have predominately right-sided adenomas. The finding is another argument that screening and diagnostic evaluations of African Americans should include a complete evaluation of the colorectum, said Dr. Giardiello.
This USPSTF review was conducted by the Oregon Evidence-based Practice Center under contract to the Agency for Healthcare Research and Quality. The review authors have disclosed no relevant financial relationships.
Ann Intern Med. Published online October 6, 2008.
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