byJustin Jackson, Phys.org

Credit: Pixabay/CC0 Public Domain

IRCCS Ospedale Policlinico San Martino with Mayo Clinic and multiple international cancer research centers have delivered a pooled analysis indicating that colon cancer recurrence risk drops below 0.5% by year six after surgery, offering a practical definition of cure.

Colon cancer relapse risk has typically incorporated end points that count deaths and second primary tumors as events, measures that can blur definitions of whether a person is actually free of relapse.

Prior work found 1.5% recurrence risk at five years and 0.5% at eight years, setting the stage for a clearer benchmark.

In the study, "The Definition of Cure in Colon Cancer,"publishedinJAMA Oncology, researchers designed a pooled analysis to separate true relapses from competing events and to determine when relapse risk becomes negligible.

The pooled population included 35,213 patients with stage II to III colon cancer enrolled across 15 Phase III randomized trials conducted between 1996 and 2015. All participants had undergone radical surgery followed byadjuvant chemotherapy, and each trial maintained a median follow-up duration of at least six years.

Incidence of relapse peaked at 6.4% between months six and 12, then declined with every six-month window below 0.5% from year 6.5 to year 10. Competing-event analysis showed that counting deaths and second primary tumors inflated apparent recurrence, with stronger distortion inolder patients.

Female patients experienced lower recurrence risk when death was modeled as a competing event, a hazard ratio (HR) of 0.58.

Age subgroups showed higher event incidence when death was treated as a competing risk for patients 40 years and older vs. younger than 40 years, HR of 2.93, with similar patterns at 50 years and at 70 years. Across the full dataset, 9,587 patients had documented local or distant recurrence during follow-up, representing 27.2% of the cohort.

Authors conclude that arelapserisk below 0.5% at six years supports a practical definition of cure in stage II to IIIcolon cancer. Adoption of this milestone could improve patient communication, guide follow-up duration, and reduce unnecessary long-term surveillance.

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More information: Alessandro Pastorino et al, The Definition of Cure in Colon Cancer, JAMA Oncology (2025). DOI: 10.1001/jamaoncol.2025.3760 Journal information: JAMA Oncology