Colorectal cancer (CRC) is the 2nd leading cause of cancer death in the United States (US), with 149,500 new CRC cases, and 52,980 deaths expected in 202119; 4,000 Veterans are diagnosed with CRC annually. Screening for CRC reduces incidence and mortality, in part due to detection and removal of polyps such as adenomas. National and VA guidelines recommend surveillance colonoscopy after adenoma removal (defined herein as polypectomy), but the incremental benefit of surveillance after polypectomy on reducing CRC incidence and mortality are uncertain. For adults age 75 and older ("older adults") considering surveillance colonoscopy, these issues are of particular importance. Harms associated with colonoscopy increase dramatically with age, with 3.8% to 6.8% of older adults experiencing an emergency visit or hospitalization within 30 days of colonoscopy. Older vs. younger adults have a 1.5 to 3.7-fold increase in post-colonoscopy complications. Older adults also are less likely to live long enough to benefit from interventions such as surveillance colonoscopy, due to competing, non-CRC mortality risks. The well-established age-related increasing risks for competing causes of mortality and colonoscopy-related harms stand in sharp contrast to major evidence gaps: it is unclear whether CRC risk is clinically significant among older adults with prior history of polyps, and whether exposing older adults to surveillance reduces CRC risk. Yet, the default clinical paradigm is for many older adults to receive surveillance colonoscopy. In the VA, surveillance is a very common indication for colonoscopy among older Veterans, with an estimated \>17,400 exposed to surveillance annually. The mismatch between available evidence and current clinical practice, coupled with extreme constraints on colonoscopy resources in the VA, make the surveillance colonoscopy paradigm an ideal focus area for quantifying risks and benefits to optimize health outcomes. The Overarching Aim is to advance knowledge on CRC risks among older adults with prior polypectomy and potential benefits of surveillance colonoscopy, with the goal of informing policies and clinical strategies that optimize benefits, risks, and resource utilization. The Specific Aims are to:

Aim 1. Compare cumulative CRC risk after age 75 in a cohort of older adults with history of normal colonoscopy (n=101,328) vs. colonoscopy with polypectomy (n=29,548) prior to age 75. After normal colonoscopy, US Preventive Services Task Force guidelines note that benefits of repeat screening in older adults are likely minimal and recommend selective screening. Finding no CRC risk difference for older adults with prior normal colonoscopy vs. polypectomy would suggest surveillance guidelines should follow a similar approach. Risk analyses will also be stratified by baseline adenoma type (low vs. high risk). Hypothesis: Cumulative risk for incident CRC (primary analysis) and fatal CRC (secondary analysis) after age 75 will be similar in older adults with normal colonoscopy vs. colonoscopy with polypectomy prior to age 75.

Aim 2. Among older adults with polypectomy prior to age 75, assess comparative effectiveness of exposure vs. no exposure to surveillance colonoscopy after age 75 for reducing CRC risk using a case-cohort design. Cases with incident (n=270) and fatal CRC (n=150), and a random sample subcohort with prior polypectomy (n=1,036) will undergo rigorous chart review to ascertain exposure to surveillance colonoscopy. Harms associated with surveillance will be characterized. Risk analyses will also be stratified by baseline adenoma type (low vs. high risk). Hypothesis: Older adults unexposed vs. exposed to surveillance will have similar risk for incident CRC (primary analysis) and fatal CRC (secondary analysis).

Aim 3. Obtain multi-level stakeholder perspectives regarding CRC risk and surveillance outcomes to inform future use and VA policy regarding surveillance colonoscopy in older Veterans. The investigators will conduct 44 semi-structured one-on-one qualitative interviews with VA patients (older adults) and providers (primary care, GI, geriatrics) to understand perspectives on CRC risk, and potential benefits and harms of surveillance (Aim 3a). The investigators will then convene an expert panel with key stakeholders including Veterans, primary providers, geriatricians, gastroenterologists, VA leaders, and policy makers to present Aim 1, 2, and 3a findings (Aim 3b). The primary outcome will be specific recommendations regarding use of surveillance colonoscopy in older adults, ranked by priority and feasibility, that can guide VA policy around future implementation (or de-implementation) of surveillance among older adults.

Impact: Establishing CRC risk among older adults with prior polypectomy, and outcomes associated with surveillance, will fill critical evidence gaps and inform guidelines within and outside VA. Multi-stakeholder perspectives on CRC risk and surveillance outcomes will pave the way for future implementation of evidence-based, Veteran-centric, and optimized value strategies for surveillance among older adults. This work will also serve as a model for leveraging VA data to address an important population health challenge for the VA's large and growing older adult population, and to use these data to engage Veterans, healthcare providers, and policy makers in identifying interventions which can be scaled and sustained to optimize outcomes.