491 Background: Uncertainty exists regarding the use of adjuvant therapy in patients with stage II colon cancer. To assist decision making, we compared quality-adjusted life expectancy and costs associated with using a multigene recurrence score (RS) assay with the use of clinicopathological factors currently recommended in clinical guidelines. Methods: A state-transition (Markov) model was developed to assess outcomes associated with the use of the RS (Oncotype Dx gene expression assay) in adjuvant therapy decisions in stage II colon cancer (excluding T4 tumors and those with deficient DNA mismatch repair). RS test characteristics were based on results reported from a randomized controlled trial (QUASAR, Kerr et al. ASCO, 2009). Current rates of administering adjuvant chemotherapy (aCTX) as a function of age, lymphatic invasion, tumor stage, and number of lymph nodes examined was derived from the NCCN Colon/Rectum Cancer Outcomes study (Earle et al, J Surg Oncol, 2009). Effects of aCTX on recurrence risk were based on published data. Medicare fee schedules were used to estimate cost; toxicities, recurrence, and quality-of-life adjustments were obtained from published studies. Results: Treatment decisions based on RS and a patient's years of life remaining without cancer recurrence would reduce aCTX use by 17% compared with current treatment patterns, and increase quality-adjusted life expectancy by an average of 0.035 years. With lower use of aCTX, direct medical costs are expected to decrease by an average of $2,971 per patient. One-way sensitivity analysis predicts overall QALY improvement with the RS through a range of variables, with the results most sensitive to the disutility associated with aCTX use. Sensitivity analyses also show the assay to be cost-saving under a variety of conditions. Conclusions: Clinical use of a multigene RS to assess risk of recurrence in T3 stage II colon cancers with intact mismatch repair is likely to improve quality-adjusted life expectancy and be cost-saving from a societal perspective. Patient age and disutility associated with chemotherapy are important considerations in adjuvant treatment decisions. [Table: see text]
Clinical implication of adjuvant chemotherapy according to mismatch repair status in patients with intermediate-risk stage II colon cancer
