ERBB2 and breast cancer: The probabilistic sensitivity analysis confirmed T-DM1 dominance in 81.2% of the 1000 Monte Carlo simulations, demonstrating consistency across settings.<h4>Conclusion</h4>T-DM1 is a cost-effective and dominant strategy for the adjuvant treatment of residual invasive HER2+ early BC in Colombia, driven by cost savings from reduced high-cost recurrences.