OBJECTIVES: Colon cancer (CC) is one of the leading cancers in the US and worldwide. Current guidelines recommend that low-risk Stage II CC patients undergo surveillance to monitor potential recurrences post-curative surgery. Despite being classified as low risk, as defined by clinicopathologic factors, these patients are still at risk of recurrence. Long-term clinical outcomes under the current practice in this population remain unclear. This study aimed to develop a lifetime comprehensive microsimulation model to capture the disease prognoses, treatments, and surveillance of these patients, offering a better evaluation of current guideline recommendations.

METHODS: A Markov-based model was developed to simulate the lifetime natural history of low-risk Stage II CC survivors starting at age 65. Published data were used to inform the disease progression rates, performance characteristics of screening modalities, and real-world screening adherence patterns. The model integrated surveillance algorithms and post-recurrence treatment options as recommended in the current guidelines. We also validated our model with the National Cancer Database records following ISPOR validation guidelines.

RESULTS: The model predicted a 12.1% chance of recurrence over 10 years in low-risk Stage II CC survivors, with 10-year overall survival of 73.2% and recurrence-free survival of 68.0%. The average life expectancy for a low-risk Stage II CC survivor was 16.7 years. The projected recurrences per 10,000 survivors in 10 years was 1,210 (380 locoregional and 830 distant). Current surveillance modalities detect only 530 of these cases, leaving 56% undetected.

CONCLUSIONS: Our microsimulation model offers predictions for clinical outcomes for low-risk Stage II colon cancer survivors, highlighting the suboptimal recurrence detection rates with current guidelines. The model is a valuable tool to identify unmet needs for future studies, such as the use of molecular residual disease testing that could better follow patients’ clinical outcomes post-curative surgery.