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Completing one or more fecal immunochemical test (FIT) screenings was associated with a lower risk of death from colorectal cancer, particularly in the left colon, according to a nested case-control study conducted across two large integrated health systems.

Looking at over 10,000 patients, completing one or more FIT screenings was associated with a 33% lower risk of death from colorectal cancer (adjusted OR 0.67, 95% CI 0.59-0.76) and a 42% lower risk in the left colon and rectum (aOR 0.58, 95% CI 0.48-0.71), reported Chyke A. Doubeni, MD, MPH, of the Ohio State University Wexner Medical Center in Columbus, and colleagues.

In stratified analyses, there was no statistically significant difference in right colon cancers (aOR 0.83, 95% CI 0.69-1.01), but the difference in the estimates between the right colon and left colon or rectum was statistically significant (P=0.01), they noted in .

"The findings support the use of strategies for coordinated and equitable large-scale population-based delivery of FIT screening with follow-up of abnormal screening results to help avert preventable premature CRC [colorectal cancer] deaths," Doubeni and team wrote.

Moreover, benefits with FIT screening were observed across racial and ethnic groups, with reduced mortality risks from colorectal cancer in Asian (aOR 0.37, 95% CI 0.23-0.59), Black (aOR 0.58, 95% CI 0.39-0.85), and white (aOR 0.71, 95% CI 0.60-0.83) patients. There was also a 22% lower risk of death among Hispanic or Latino adults, but this finding was not significant (aOR 0.78, 95% CI 0.57-1.08).

The U.S. Preventive Services Task Force (USPSTF) recommends annual FIT screening among average-risk adults to reduce the risk of death from colorectal cancer. Of note, this study was conducted before the USPSTF recommended that colorectal cancer screening start at age 45 years. Because of this, findings may not directly apply to people ages 45 to 49, the authors noted.

Doubeni and colleagues explained that FIT has "several practical advantages" over guaiac-based fecal occult blood testing (g-FOBT), which has also been shown to reduce the risk of mortality from colorectal cancer. In addition to improved adherence, FIT is more sensitive for both colorectal cancer and adenomas than g-FOBT, and is also highly specific, they pointed out.

While FIT screening programs have reported from colorectal cancer, evidence on effectiveness has been limited.

For this study, Doubeni and colleagues looked at screening-eligible patients from Kaiser Permanente Northern California and Kaiser Permanente Southern California, which started colorectal cancer screening programs in 2006 and 2007, respectively, using proactive outreach with FIT for those who were not up to date for screening. All members who had a positive FIT were referred by their health system for follow-up testing and care until clinical resolution.

The authors included 1,103 case patients ages 52 to 85 years who died from colorectal adenocarcinoma from 2011 through 2017, who were matched in a 1:8 ratio based on age, sex, health plan membership duration, and geographic area to randomly selected adults (n=9,608) who were alive and without colorectal cancer on the case patient's diagnosis date.

"This approach enabled comparable periods of screening eligibility among case and control persons prior to the date of CRC diagnosis," they wrote.

Of the total group of 10,711 participants, 32.9% were ages 60-69, 52.1% were men, 59.2% were white, 18% were Hispanic or Latino, 9.1% were Black, and 11.7% were Asian.

Of the control patients during the 10-year period before the reference date, 63.5% completed one or more FIT screenings, with a cumulative 12.6% positivity rate (768 controls), of whom 79.4% had a colonoscopy within a year. During the 5-year period, 44.8% of case patients and 55.6% of control patients completed one or more FIT tests.

"Although our findings may underestimate the effectiveness of FIT under conditions of perfect adherence, they reflect benefits likely to be observed in organized population-based screening but may not directly apply to populations with lower screening or follow-up colonoscopy adherence," the authors noted.

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