Patients who died from colorectal cancer were significantly more likely than controls not to have been screened, to have missed screenings, or not to have followed up on an abnormal result, according to the results of a large retrospective case-control study.

The findings signify “potentially modifiable” screening failures in a population known for relatively high uptake of colorectal cancer screening, wrote Chyke A. Doubeni, MD, MPH, of the University of Pennsylvania, Philadelphia, and his associates in Gastroenterology. Strikingly, 76% of patients who died from colorectal cancer were not current on screening versus 55% of cancer-free patients, they said. Being up to date on screening decreased the odds of dying from colorectal cancer by 62% (odds ratio, 0.38; 95% confidence interval, 0.33-0.44), even after adjustment for race, ethnicity, socioeconomic status, comorbidities, and frequency of contact with primary care providers, they added.

Colonoscopy, sigmoidoscopy, and fecal testing are effective and recommended screening techniques that help prevent deaths from colorectal cancer. Therefore, most such deaths are thought to result from “breakdowns in the screening process,” the researchers wrote. However, interval cancers and missed lesions also play a role, and no prior study has examined detailed screening histories and their association with colorectal cancer mortality.

Accordingly, the researchers reviewed medical records and registry data for 1,750 enrollees in the Kaiser Permanente Northern and Southern California systems who died from colorectal cancer during 2002-2012 and were part of the health plan for at least 5 years before their cancer diagnosis. They compared these patients with 3,486 cancer-free controls matched by age, sex, study site, and numbers of years enrolled in the health plan. Patients were considered up to date on screening if they were screened at intervals recommended by the 2008 multisociety colorectal cancer screening guidelines – that is, if they had received a colonoscopy within 10 years of colorectal cancer diagnosis or sigmoidoscopy or barium enema within 5 years of it. For fecal testing, the investigators used a 2-year interval based on its efficacy in clinical trials.

Among patients who died from colorectal cancer, only 24% were up to date on screening versus 45% of cancer-free-patients, the investigators determined. Furthermore, 68% of patients who died from colorectal cancer were never screened or were not screened at appropriate intervals, compared with 53% of cancer-free patients.

Additionally, while 8% of colorectal cancer deaths occurred in patients who had not followed up on abnormal screening results, only 2% of controls who had received abnormal screening results had failed to follow up.

“In two health systems with high rates of screening, we observed that most patients dying from colorectal cancer had potentially modifiable failures of the screening process,” the researchers concluded. “This study suggests that, even in settings with high screening uptake, access to and timely uptake of screening, regular rescreening, appropriate use of testing given patient characteristics, completion of timely diagnostic testing when screening is positive, and improving the effectiveness of screening tests, particularly for right colon cancer, remain important areas of focus for further decreasing colorectal cancer deaths.”

The National Institutes of Health funded the work. The investigators reported having no conflicts of interest except that one coinvestigator is editor in chief of the journal Gastroenterology.

SOURCE: Doubeni CA et al. Gastroenterology. 2018 Sep 27. doi: 10.1053/j.gastro.2018.09.040.