medwireNews: Delaying follow-up colonoscopy for up to 10 months after a positive fecal immunochemical test (FIT) is not associated with a significantly increased risk for colorectal cancer and more advanced disease, US study data show.
Longer delays, however, are linked to 1.5- to 3.2-fold increased risks for these outcomes, but “[f]urther research is needed to assess whether this relationship is causal,” the researchers report in JAMA.
The retrospective cohort study, conducted by Douglas Corley (Kaiser Permanente Northern California, Oakland) and colleagues included data for 70,124 patients aged 50–75 years with positive FIT results who had a follow-up colonoscopy.
Overall, there were 2191 cases of any colorectal adenocarcinoma and 601 cases of advanced (stage III and IV) disease detected, with colonoscopy conducted a median 37 days after a positive FIT.
Corley and team found that each 30-day interval after the first 8–30 days was associated with an approximate 3% increased risk for any colorectal cancer and a 5% increased risk for advanced-stage disease.
However, the differences were not significantly different for patients followed up at 2 months (n=24,644), 3 months (n=8666), 4 to 6 months (n=5251), or 7 to 9 months (n=1335), compared with those followed up within 8 to 30 days (n=27,176). The respective colorectal cancer incidence rates per 1000 patients were 28, 31, 31, 43, and 30, while those for advanced stage disease were 7, 7, 9, 13, and 8.
By contrast, patients who underwent colonoscopy 10–12 months after a positive FIT (n=748) had a significant 1.5-fold increased odds for any colorectal cancer (49 cases per 1000 patients) and a 2.0-fold increased odds for advanced stage disease (19 cases per 1000 patients) compared with those followed up within 8 to 30 days.
Patients with a follow-up delay of more than 12 months (n=747) had the greatest risk increase, with odds ratios for any colorectal cancer and advanced-stage disease of 2.3 and 3.2, respectively, and incidence rates of 76 and 31 cases per 1000 patients.
In an accompanying editorial, Carolyn Rutter (RAND Corporation, Santa Monica, California, USA) and John Inadomi (University of Washington School of Medicine, Seattle, USA) say that the study “provides important reassurance for patients and physicians.”
“The findings indicate that there is no immediate need to rush to have a colonoscopy after a positive FIT result, reflecting the clinical understanding that colorectal cancer is a disease that generally develops slowly,” they write.
However, they add that “the duration of the ‘safe window’ until colonoscopy for which maximal benefit is still achieved” is a “clinically relevant” question that needs to be answered.
Rutter and Inadomi conclude: “For most patients with a positive FIT screening result, sooner is probably better for follow-up colonoscopy because cancer risk increases over time, but increases slowly.
“Practically, an important reason for a shorter interval for follow-up colonoscopy is a reduction in the risk of losing contact with patients.”
By Laura Cowen
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