At-home tests, which measure blood in stool as a potential marker for colon cancer, are often used for colorectal cancer screening. Usage of these tests has increased during the COVID-19 pandemic as patients try to avoid clinical visits. However, effectiveness of these screening tools, along with all colon cancer screenings, requires a follow-up colonoscopy if an abnormal test result occurs. The problem is that experts say current follow-up rates are low.
A study published by San Miguel et al in Gastroenterology found delayed time between abnormal stool-based screening and subsequent colonoscopy was associated with an increased risk of a cancer diagnosis and death from colorectal cancer.
The study found those who delayed a colonoscopy by more than 12 months after an abnormal screening test result were at an increased risk of being diagnosed with colorectal cancer. The odds of being diagnosed with late-stage colon cancer increased at 16 months by approximately 33%.
“Many colon cancers are asymptomatic and can be growing without the patient even knowing. That is why it is so important to screen. But as our study shows, it is also critical to follow up with a colonoscopy if the screening result is abnormal,” said corresponding study author Samir Gupta, MD, Professor of Medicine in the Division of Gastroenterology at the University of California San Diego School of Medicine and VA San Diego Healthcare System.
Samir Gupta, MD
“Early detection means less invasive treatments and excellent outcomes. When detected early, patients have a 90% survival rate with a low risk of recurrence. Late-stage colorectal cancer means more invasive and complex treatment, with less than a 15% survival rate. As usage of more noninvasive tests for colorectal cancer screening continue to rise during the pandemic, and as more noninvasive screening tests come onto the market in the future, it is critical to ensure all patients with abnormal colorectal cancer screening tests get a timely colonoscopy,” he said.
More Study Details
The national study involved 204,733 veterans aged 50 to 75 (mean age = 61) who had received an abnormal screening test result. A limitation of the study was a high proportion of men; 5,453 women were included.
Compared to patients who received a colonoscopy at 1 to 3 months after an abnormal screening result, there was an increased colorectal cancer risk for patients who received a colonoscopy at: 13 to 15 months post–abnormal result, 16 to 18 months, 19 to 21 months, and 22 to 24 months. Odds of being diagnosed with late-stage disease increased at 16 months.
“There are no national standards or mandates to guide patients, providers, or health-care systems on the clinically acceptable period of time between abnormal screening and colonoscopy,” said senior study author Folasade May, MD, PhD, Assistant Professor of Medicine at the University of California Los Angeles. “We hope our findings will inform national standards for appropriate time intervals and interventions to improve timely colonoscopies and colorectal cancer outcomes.”
A family history, smoking, and poor diet are significant risk factors of colon cancer. Symptoms include rectal bleeding, low-iron anemia, a change in bowel habits, and unexplained weight loss.
In 2018, the American Cancer Society updated guidelines for colorectal cancer screening. It is now recommended that those aged 45 with an average risk of colon cancer begin regular screenings; previously, the guideline recommended screening begin at age 50 for people at average risk.
“In general, prevention and early detection efforts have substantially dropped death rates in the United States. However, the pandemic has resulted in many people missing cancer screenings or not doing follow-up colonoscopies after abnormal at-home screenings,” said Dr. Gupta. “We strongly encourage patients to schedule an appointment if they receive an abnormal screening test. Our hospital and clinical settings are following all COVID-19 safety guidelines. Hesitancy to follow up on your health care could have fatal consequences.”
Disclosure: Funding support for this research came in part from the National Institutes of Health and the Department of Veterans Affairs Health Services Research and Development. For full disclosures of the study authors, visit gastrojournal.org.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.