A delay of one year or longer in diagnostic colonoscopy after an abnormal stool-based screening test was significantly associated with the incidence of colorectal cancer, advanced stage at diagnosis and mortality, researchers have found.
The analysis of more than 204,000 U.S. veterans with abnormal results on the fecal occult blood test (FOBT) or fecal immunochemical test (FIT) found that the risk for one of those adverse outcomes was higher if diagnostic colonoscopy was delayed 13 to 24 months after the initial screening. Compared with patients who underwent colonoscopy one to three months after FOBT or FIT, those whose colonoscopy occurred 13 to 24 months later were 1.1 to 1.3 times more likely to be diagnosed with CRC, the researchers reported. The risk for CRC-related mortality increased 1.4 to 1.5 times when colonoscopy was delayed by 19 to 24 months, and the odds of advanced stage at diagnosis were 1.3 to 1.7 times higher when colonoscopy was delayed beyond 16 months, according to the study. The research was published in February in Gastroenterology.
Use of at-home stool-based testing has increased during the COVID-19 pandemic, as clinic visits declined. A recent study from the University of Pennsylvania showed 140 fewer new patient visits and almost 10,000 fewer colonoscopies performed during 2020, compared with the year before.
“As the use of more noninvasive tests for colorectal cancer screening continues to rise during the pandemic, and as more noninvasive screening tests come to the market in the future, it’s critical to ensure all patients with abnormal test results get a timely colonoscopy,” said Samir Gupta, MD, a professor of medicine at the University of California, San Diego, and the chief of the GI section at the San Diego Veterans Affairs Healthcare System, who helped conduct the latest study.
National Study of Veterans
Existing data examining time to colonoscopy and subsequent risks support a range of follow-up intervals. However, no national policy or standard exists, the authors said.
The national retrospective study involved 204,733 veterans, mostly men, ages 50 to 75 years (mean age, 61 years) with an abnormal FOBT or FIT result between 1999 and 2010. To identify associations between time to colonoscopy and CRC outcomes, the researchers calculated CRC-specific incidence and mortality hazard ratios (HRs) for three-month colonoscopy intervals, with one to three months as the reference group. All multivariable models adjusted for age at time of cancer screening, sex, race and ethnicity, tobacco use, body mass index and comorbidities.
Compared with patients who received a diagnostic colonoscopy one to three months after an abnormal test result, the risk for CRC was elevated for patients with colonoscopies at 13 to 15 months (HR, 1.13), 16 to 18 months (HR, 1.25), 19 to 21 months (HR, 1.28), and 22 to 24 months (HR, 1.26) later.
The mortality risk from CRC was higher for patients receiving a colonoscopy after 19 to 21 months (HR, 1.52) and after 22 to 24 months (HR, 1.39). The researchers observed no differences in the risk for CRC-related mortality for patients with a colonoscopy at the other time intervals. The odds for having late-stage CRC increased at 16 months.
In contrast, the risk for incident CRC was lower for patients who underwent colonoscopy four to six months (HR, 0.91) and seven to nine months (HR, 0.89) after the initial screening, as well as after 24 months (HR, 0.86).
Finally, a multivariable logistic regression model showed that, compared with patients diagnosed with CRC at an early stage, the odds of being diagnosed with advanced-stage cancer increased when colonoscopy was delayed to 16 to 18 months (odds ratio [OR], 1.33), 19 to 21 months (OR, 1.51), and 22 to 24 months (OR, 1.66).
The temporal differences were statistically significant (P<0.05), according to the researchers.
Implications and Recommendations
The findings indicate the largest burden of CRC cases and deaths occurs when colonoscopy is delayed several months after abnormal FIT or FOBT, the authors wrote, acknowledging that there are advantages and disadvantages to various intervals.
“[A] recommended interval that is too long can contribute to polyp progression and stage migration of CRC, risking the need for more aggressive and morbid treatment, as well as less favorable outcomes. However, too short of a time interval could place undue burden on the patient and healthcare system,” they wrote. Therefore, “the strategy should be to intervene with colonoscopy well before 13 months and closer to 6 months after abnormal FIT.”
Folasade May, MD, PhD, an assistant professor of medicine and the director of the Melvin and Bren Simon Gastroenterology Quality Improvement Program at UCLA, and senior author of the study, said: “The most essential takeaway from the piece is that follow-up about abnormal results is critical to reduce the overall burden of colorectal cancer. Providers must emphasize for their patients that FIT and FOBT are a two-step process.”
“We hope our work will inform guidelines and standard of care for patients who undergo stool-based CRC screening,” Dr. Gupta added. “This guidance is especially relevant now in the setting of the COVID-19 pandemic and recommendations to increase use of non-colonoscopic screening modalities.”
Schedule ‘Well Before Risk Starts’
Douglas Corley, MD, PhD, a gastroenterologist and the director of Delivery Science and Applied Research at Kaiser Permanente of Northern California, stressed that prompt evaluation and diagnostic workup for abnormal findings is “a central tenet of cancer screening.” However, he asked: “What is ‘prompt’? A week? A month? Longer? How can we create evidence-based recommendations for how urgent follow-up is needed?”
Dr. Corley said the study adds to other data indicating adverse outcomes start trending upward after about six to 12 months of follow-up. This finding suggests patients have some time to make arrangements, but colonoscopy should be done “well before” risk starts increasing, ideally within a few months. “There are no harms for early completion, and long delays will increase the risk of less curable disease and intercurrent events, such as changes in health insurance coverage, that may interfere with follow-up altogether,” he said.
—Caroline Helwick
Drs. Corley, Gupta and May reported no relevant financial disclosures.
This article is from the June 2021 print issue.