Benefits of screening colonoscopy in very elderly may be limited

Newswise — Even though the prevalence of colon tumors increases with age, screening colonoscopy in patients over 80 years of age results in smaller gains in life expectancy, compared to younger patients, according to a study in the May 24/31 issue of JAMA.

Current guidelines recommend colorectal cancer (CRC) screening for all patients 50 years or older, but do not specify an age limit above which screening is not recommended. The number of screening colonoscopies in elderly U.S. patients has increased dramatically since Medicare coverage was approved in 2001, according to background information in the article. However, some clinicians may have concerns with regard to screening extremely elderly patients, especially when an invasive procedure such as colonoscopy is used. Colonoscopy in very elderly patients is associated with lower procedural completion rates and possibly higher complication rates. In addition, very elderly patients have shorter life expectancies, potentially limiting the benefits of screening procedures. Decisions concerning undergoing a colonoscopy are being based on limited data regarding its impact on life expectancy.

Otto S. Lin, M.D., M.Sc., of Virginia Mason Medical Center, Seattle, and colleagues conducted a study to estimate the average extension in life expectancy in very elderly vs. younger patients undergoing screening colonoscopy. The study included 1,244 asymptomatic individuals in 3 age groups (50 to 54 years, n = 1,034; 75 to 79 years, n = 149; and 80 years and older, n = 63) who underwent screening colonoscopy.

The researchers found that the prevalence of colon neoplasia increased with age. Participants aged 80 years or older had a significantly higher prevalence of advanced neoplasia than the 50- to 54-year-old group (14 percent vs. 3.2 percent). Baseline average life expectancy was lower in the 2 older age groups vs. the 50- to 54-year-old group. Because of this, despite the higher prevalence of advanced neoplasia in elderly patients, the average extension of life expectancy was much lower in the 2 elderly groups. The group aged 80 years or older had a average extension of life expectancy of only 0.13 years, compared with 0.85 years for the 50- to 54-year-old group, a 6.5-fold difference.

“The results reported here show that even though the prevalence of colonic neoplasia increases with age, screening colonoscopy in very elderly patients results in only 15 percent of the expected gain in life expectancy achieved in younger patients,” the authors write. “These data suggest that the benefit of screening colonoscopy in very elderly patients may be smaller than what is commonly believed. This should help individual patients and clinicians decide whether screening colonoscopy should be performed and help avoid its use in patients who are unlikely to benefit substantively.”

Patients with a negative colonoscopy examination have a reduced risk of developing colorectal cancer for more than 10 years, compared to the general population, according to a study in the May 24/31 issue of JAMA.

Colorectal cancer is the third most commonly diagnosed cancer and the second leading cause of cancer deaths in North America. Screening for CRC and its precursor lesions has become an increasingly prevalent practice. Colonoscopy has been recommended as the preferred initial screening test by several medical organizations and is being widely performed in the United States for screening among average-risk individuals. Colonoscopy allows for removal of most precancerous polyps at the time of detection. A screening interval of 10 years after a normal colonoscopy has been adopted based on the estimate of the time it takes for an adenomatous (benign tumor) polyp to transform into carcinoma. However, the duration over which the risk of CRC remains decreased following the performance of a normal colonoscopy has been unknown.

Harminder Singh, M.D., of the University of Manitoba, Canada, and colleagues analyzed data from individuals who underwent a colonoscopic evaluation that did not result in the diagnosis of colorectal neoplasia to determine the magnitude and duration of their lowered risk of developing CRC. The patients (n = 35,975), who had been evaluated between April 1989 and December 2003, were identified using Manitoba Health’s physician billing claims database. Standardized incidence ratios (SIRs) were calculated to compare colorectal cancer incidence in this group with colorectal cancer incidence in the provincial population. The patients were followed up from the time of the colonoscopy until diagnosis of colorectal cancer, death, moving from Manitoba, or end of the study period on December 31, 2003.

The researchers found that a negative colonoscopy was associated with SIRs of 0.69 (31 percent lower incidence of CRC compared to general population) at 6 months, 0.66 (34 percent lower incidence) at 1 year, 0.59 (41 percent lower incidence) at 2 years, 0.55 (45 percent lower incidence) at 5 years, and 0.28 (72 percent lower incidence) at 10 years. The proportion of colorectal cancer located in the right side of the colon was significantly higher in the colonoscopy group than the rate in the Manitoba population (47 percent vs. 28 percent).

“This study demonstrates that following a negative result from a colonoscopy performed in the usual clinical practice, the risk of developing CRC is at most 60 percent to 70 percent of the risk of developing CRC in the general population and the duration of the interval of decreased CRC risk persists for more than 10 years. Furthermore, if an individual undergoes a single negative colonoscopy, excepting any follow-up endoscopies at which CRC is diagnosed, the risk of developing CRC is even lower and the duration of the interval of decreased risk again exceeds the 10-year interval currently recommended between screening colonoscopies. Our findings suggest that screening colonoscopies do not need to be performed at intervals shorter than 10 years,” the authors conclude.