Why Adenoma Detection Rate Matters in Colorectal Cancer Screening

·10 min·1 clip

A 2025 study of 1.7 million colonoscopies reveals how a doctor's adenoma detection rate directly impacts finding cancer.

The episode begins with host Dr. Brian McDonough introducing the topic: a recent report published in Gastroenterology in 2025 titled 'Association Between Adenoma Detection Rate and Prevalent Colorectal Cancer Detection Rate in a National Colonoscopy Registry.' He is joined by guest Dr. Renee Williams, a professor of medicine and associate chair for health equity at NYU Grossman School of Medicine. The study analyzed over 1.7 million colonoscopies from the GI-QUIC registry, involving 3,500 endoscopists, to investigate the relationship between an endoscopist's adenoma detection rate (ADR) and their ability to detect colorectal cancer during screening colonoscopies. Dr. Williams explains that ADR is a validated quality metric known to correlate with lower post-colonoscopy cancer risk. The host then delves into the key results: screening colonoscopies performed by endoscopists in the highest ADR quintile detected about 33 cancers per 10,000 procedures, compared to roughly 27 per 10,000 in the lowest quintile. Dr. Williams interprets this, stating it makes sense that higher ADR leads to higher cancer detection, as missing polyps often means missing cancer. She notes recent changes in quality metrics, such as increasing withdrawal time from six to eight minutes for normal colons, to improve detection. The discussion turns to the estimated 20-33% of cancers that may be missed by endoscopists with the lowest ADRs. Dr. Williams contextualizes this, mentioning that colonoscopy specificity is about 90%, so missing 10% of cancers is commonly discussed, but this study suggests a higher potential miss rate. She attributes this to operator dependency and the difficulty of detecting subtle, flat lesions like sessile serrated lesions, which have a faster pathway to cancer. The episode then examines findings from colonoscopies performed after abnormal stool-based tests, such as fecal immunochemical tests (FIT) or stool DNA tests. Cancer detection rates were substantially higher in this setting, ranging from 108 to 165 cancers per 10,000 depending on ADR level. Dr. Williams stresses the importance of timely colonoscopy within six months after a positive stool test, citing a Taiwanese study showing increased risk after six months. She highlights that the ADR benchmark for positive stool tests is about 50%, meaning half the time an endoscopist should find a polyp or cancer. The conversation explores how stool-based tests and colonoscopy can work together to improve detection. Dr. Williams notes that stool-based options provide choice for patients who may avoid colonoscopy due to the prep. A positive stool test can drive patients to timely diagnostic colonoscopy, but there is often a fall-off where patients do not follow up. She emphasizes the need for organized outreach to ensure completion. Throughout, Dr. Williams underscores that colonoscopy outcomes are operator-dependent, and endoscopists should know their ADR for quality improvement. In the final segment, she offers key takeaways for clinicians: perform risk assessment to guide test selection, use colonoscopy for high-risk patients (e.g., family history, IBD, Lynch syndrome), and ensure a positive stool test is followed by a timely colonoscopy to close the care loop. The episode concludes with thanks and sponsorship acknowledgments.

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