Colorectal cancer screening and management in the aging society: a narrative review of benefit, risk, and the biological imperative for rural and community medicine

抄録

Objective: As the global population ages, colorectal cancer screening among elderly individuals has become an increasingly debated issue, particularly in resource-limited rural settings. This review aimed to synthesize the current evidence regarding the benefits and risks of screening in older cohorts to guide community practice.

Materials and Methods: We critically analyzed the literature on fecal immunochemical testing, colonoscopy, and polypectomy, emphasizing the geriatric paradox, in which cancer risk peaks as physiological reserve declines. We compared the international and Japanese guidelines for the “10-year rule” and “lag time to benefit”.

Results: Fecal immunochemical testing specificity often declined in the elderly, in part owing to anticoagulant use and diverticulosis, which can trigger unnecessary high-risk diagnostic cascades. The incidence of colonoscopy complications increases significantly with age. Because the mortality reduction benefit of screening takes approximately 10 years, it often exceeds the life expectancy of frail patients. Reliance on chronological age is obsolete; assessments should instead prioritize biological health using validated tools such as the Schonberg Index.

Conclusion: A paradigm shift toward precision screening based on biological reality and shared decision-making is essential. In rural medicine, avoiding overdiagnosis and preserving the quality of life of patients with limited physiological reserves must be prioritized over detecting low-risk lesions.