One of the main quality metrics for colonoscopy in the general population is the adenoma detection rate (ADR), which is inversely correlated with post-colonoscopy colorectal cancer (PCCRC). However, in Lynch Syndrome (LS), the most common inherited syndrome predisposing to CRC, ADR has not been defined, and no quality metric is used currently in clinical practice. To address this gap, our aims were 1) to determine ADR, advanced ADR (AADR) and CRC rates in LS patients for both index and surveillance colonoscopies, and 2) to correlate ADR and AADR to PCCRC in LS patients in order to establish a quality metric in this patient population.

A retrospective cohort study including patients with a defined LS-associated gene mutation (MLH1, MSH2, MSH6, PMS2 or EPCAM) from 5 healthcare centers in the US was performed. Patients with inflammatory bowel disease or other inherited CRC syndromes were excluded. Polyp detection metrics were ADR, AADR, and CRC detection rates. Colonoscopy quality metrics were measured for surveillance intervals (<24 months (within 2 years), 24-48 months (2-4 years), and ≥49 months (more than 4 years)). Fisher’s Exact test was used to compare detection rates.

In total, 307 LS patients underwent index colonoscopy, and, of these, 202 had at least 1 surveillance colonoscopy. The distribution of mutations was: MLH1 24.0%, MSH2 27.8%, MSH6 30.7%, PMS2 15.9% and EPCAM 1.6%. ADR, AADR and CRC detection rates at index colonoscopy were 40%, 20%, and 13%, respectively. The ADR, AADR, and CRC detection rates per surveillance colonoscopy were 26%, 6%, and 1%, respectively. ADR was similar for surveillance colonoscopies performed at 0-24 months, 24-48 months or more than 48 months (25%, 30%, and 26% respectively, p>0.05). AADR was significantly higher in ≥49 months interval compared to 0-24 months (16% and 5% respectively, p=0.0205) and CRC rates increased significantly between 0-24 months and 24-48 months (3% and 0% respectively, p=0.0026) and ≥49 months intervals (10% and 0% respectively, p=0.0003).

Results from this study estimate ADR, AADR and CRC rate in LS patients and demonstrate increase in rates with prolonged surveillance intervals. The current sample size limits assessment of ADR and PCCRC correlation. A larger cohort is planned to correlate ADR and PCCRC and to establish evidence-based colonoscopy quality metrics in LS patients.

Joshua Melson

Banner - University Medical Center Tucson

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