When is colonoscopy necessary? - Distal-proximal adenoma relationships in the polyp prevention trial (PPT)

The need for colonoscopy in individuals with low risk distal adenomas found on sigmoidosocopy is a controversial and important screening issue. AIM: To examine the prevalence of advanced (adv) proximal adenomas in patients (pts) with non-advanced distal adenomas in a large cohort with central pathologic review. METHODS: The PPT is a multi-center randomized study (N=2079) of dietary intervention on adenoma recurrence. Using the index colonoscopy prior to randomization, pts with distal adenomas (distal to splenic flexure or ≤50 cm) and no prior history of adenoma or previous colonsocopy were included (N=1123). Relationships between distal and adv proximal adenomas were examined. RESULTS: Mean age 60, 38% female, 10% minority. 45.6% of the distal polyps (512/1123) were adv, i.e., had a villous component, HG Dysplasia (HGD), or were ≥1cm. 18.7% (48/257) of the proximal adenomas were adv. 4.3% of all patients had an adv proximal adenoma (48/1123). Villous Histology: 2.9% of pts with distal villous compared to 1.4% of pts w/o distal villous had a proximal villous lesion (OR 2.1, p=NS). HGD: 3.5% of pts with distal HGD compared to 0.8% of pts w/o distal HGD had proximal HGD (OR 4.8, p=.03). ≥1cm: 4.2% of pts with distal ≥1cm compared to 3.0% of pts w/o distal ≥1cm had a proximal ≥1cm lesion (OR 1.4, p=NS). Overall, 5.7% of pts (29/512) with a distal adv lesion compared to 3.1% of pts (19/611) w/o a distal adv lesion had a proximal adv lesion (OR 1.9, 95%CI 1.0, 3.5, p=.05). Altering the definition of a distal/proximal lesion did not change the results. CONCLUSIONS: 1) Pts with an adv distal adenoma are about twice as likely to have an adv proximal adenoma. 2) 3.1% of pts w/o an adv distal adenoma had an adv proximal adenoma. Not performing a colonoscopy in patients with a distal non-adv adenoma in this cohort would have missed 40% (19/48) of the proximal adv adenomas. 3) These results support performing a colonoscopy in pts with a non-adv distal adenoma found on flexible sigmoidoscopy.