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Negative colonoscopy linked to lower colorectal cancer risk after 12 years
Average risk patients with a negative colonoscopy demonstrated a lower risk for overall, proximal, distal, early-stage and advanced-stage colorectal cancer and related deaths for more than 12 years after screening, according to findings published in JAMA Internal Medicine.
“Guidelines recommend a 10-year rescreening interval after a colonoscopy with normal findings (negative colonoscopy results), but evidence supporting this recommendation is limited,” Jeffrey K. Lee, MD, MAS, from the department of gastroenterology at Kaiser Permanente San Francisco, and colleagues wrote.
Lee and colleagues conducted a retrospective cohort study to compare the long-term risks of colorectal cancer and colorectal cancer deaths in patients with a negative colonoscopy vs. unscreened patients. The researchers enrolled 1,251,318 average-risk screening-eligible patients between the ages of 50 and 75 years between Jan. 1, 1998, and Dec. 31, 2015 (49% men; mean age, 55.6 years).
Colorectal screening was assessed as a time-varying exposure. All participants contributed person-time unscreened until they were either screened by fecal test, sigmoidoscopy or colonoscopy or censored, defined as dying, being diagnosed with colorectal cancer, having a health plan membership terminated or reaching the end of the study. Participants with a negative colonoscopy contributed person-time in the negative colonoscopy results group until they were censored.
The analysis was adjusted for age, sex, race/ethnicity, Charlson comorbidity score and BMI. Over more than 12 years of follow-up, the risk for colorectal cancer and related deaths was lower among participants with a negative colonoscopy result compared with those who were unscreened.
A total of 5,743 colorectal cancers were diagnosed; of which, 31.7% were proximal cancers and 45.1% were advanced-stage cancers.
At the current guideline-recommended 10-year rescreening interval, the risk for colorectal cancer was 46% lower (HR = 0.54; 95% CI, 0.31-0.94) and the risk for related deaths was 88% lower (HR = 0.12; 95% CI, 0.02-0.82).
The risk of proximal colorectal cancer was 20% to 87% lower and the risk of distal cancer was 50% to 99% lower in the negative colonoscopy results group during follow-up versus the unscreened group.
“Our findings can inform guideline recommendations for rescreening and future studies to evaluate the costs and benefits of earlier vs. later rescreening intervals,” Lee and colleagues concluded. – by Alaina Tedesco
Disclosures: The authors report no relevant financial disclosures.
Perspective
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This is a methodologically rigorous study with compelling findings. Previous observational studies have assessed the risk of colorectal cancer after negative screening colonoscopy, but none have had sufficient power to allow estimation of annual colorectal cancer incidence and mortality rates, compared to unscreened cohorts.
The findings of lower risk of overall, proximal, distal, early and advanced colorectal cancer for more than 12 years after screening are reassuring and confirm current paradigms. The study also raises the interesting possibility of making rescreening recommendations based on pre-specified colorectal cancer risk thresholds.
Several studies have shown that many clinicians recommend inappropriately frequent colonoscopy in average-risk patients, a practice which increases costs and subjects patients to unnecessary risk. This study’s findings are further evidence that average-risk patients who undergo high-quality screening colonoscopy with no polyps can be rescreened in 10 years.
The findings reaffirm current guidelines.
Perspective
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This study by Lee et al is elegant, well-designed, and affirms the importance of colonoscopy in preventing colorectal cancer. It is generally accepted that a negative colonoscopy decreases subsequent colon cancer risk, and these findings validate that hypothesis as the reduction was pronounced and was seen in a large cohort of patients who were followed over a very long time period.
It is especially heartening that the authors found a substantial decrease in mortality from colorectal cancer as this has not been well-documented to date. It is also encouraging that screening with colonoscopy decreased the number of proximal colon cancers found. The fact that the decrease was not as great as the reduction in distal cancers is not surprising but nonetheless mildly disappointing.
The main takeaway from this study for endoscopists is the importance of making sure they are performing high-quality colonoscopies in their practices. In order to reap the benefits shown here, it is important to educate patients about the importance of good bowel preparation and for endoscopists to have high adenoma detection rates. This will give confidence to both providers and patients after a negative screening colonoscopy.
It is too early to say what implications this paper could have on follow-up after normal colonoscopy. Further data are likely needed in order to validate these findings. In addition to risk stratifying patients based on a negative colonoscopy, policymakers will also have to take into account recommendations from some about starting screening at 45 when constructing new guidelines.