For decades, May 3 -- the colonoscopy. Long treated as a routine safeguard against colorectal cancer, the procedure is now at the center of a more uncomfortable question in clinical practice, when, exactly, should it stop?

begin at 45, repeat at regular intervals, and continue into older age if no major contraindications emerged. That simplicity is dissolving. In its place is a more conditional framework built around physiology, life expectancy, and competing medical risks.

At the heart of this shift is guidance from the US Preventive Services Task Force colorectal cancer screening guidelines, which recommend routine screening through age 75, followed by individualized decision-making between 76 and 85. Beyond that range, screening is g...