A new prognostic and predictive tool to enhance shared decision making in stage III colon cancer.

Abstract

4010 Background: Survival outcomes in patients with stage III colon cancer varies widely according to T-N sub-stages. The ability to estimate the benefit of each therapeutic option (surgery alone, fluoropyrimidines alone, oxaliplatin-based doublet for either 3 or 6 months) in each T-N subgroup within stage III, may provide more accurate information helping doctors and patients in the complex shared decision-making process surrounding adjuvant therapy. Methods: Theoutcomedata of 12,834 patients with stage III colon cancer enrolled in the IDEA trial served as our database. Patients were categorized in 16 sub-stages, based on the T-N categories. We created a meta-regression model to predict the expected 3-year DFS within each T-N sub-stage and hence the 5-year DFS rates were projected. We then evaluated the efficacy of each therapeutic option in every sub-stage, working backward by subtraction, using an average of the HRs reported in the pertinent trials publication as conversion factor. Results: Large differences in 3-year DFS rate were observed among the subgroups, ranging from 95% (T1N1a) to 29% (T4N2b) in the overall population. The contribution to outcome of each therapeutic option in this setting varied widely across sub-stages. According to our model, patients with T1N1a cancers have a projected 5-year DFS of 85% with surgery alone. Adjuvant fluoropyrimidine alone results in 4.2% absolute DFS gain; an additional 1.7% and 0.6% gain is seen with oxaliplatin for 3 and 6 months, respectively. Patients with T4N2b cancers show a 4.7% 5-year DFS with surgery alone, and a 7.1%, 5.0%, 2.1% increase with the aforementioned adjuvant options, respectively. Conclusions: The resulting overlay bar graph gives patients and doctors the projected relative benefit of each treatment option and may substantially help the shared decision-making process.