Abstract BACKGROUND: Urothelial carcinomas presenting T1G3 non muscle-invasive lesions are high-risk tumors because of the high recurrence and progression to muscle invasive disease rates. The Bacillus of Calmette-Guérin (BCG) is a standard treatment to reduce tumor recurrence and delay progression of high-risk non-muscle invasive bladder tumors. However, it is not clear yet which T1G3 patients are more prone to display a more aggressive clinical behavior or be susceptible to respond to BCG. OBJECTIVE: The aim of this study was to evaluate the role of myopodin methylation as a clinical outcome prognosticator and predictive biomarker for BCG response in patients with T1G3 bladder tumors. DESIGN, SETTING, AND PARTICIPANTS: The methylation status of myopodin was analyzed on tumor specimens belonging to 170 patients with T1G3 non-muscle invasive bladder cancer, being a subset of them undergoing BCG treatment (n=108). MEASUREMENTS: Myopodin methylation was assessed by methylation-specific polymerase chain reactions. Recurrence, progression into muscle invasive tumors and disease-specific overall survival rates were analyzed using competing risks regression analysis. RESULTS: Among the 170 cases analyzed, 72 of them recurred (42.4%), 36 progressed (21.2%), and 24 died of the disease (14.1%). Univariate and multivariate survival analyses revealed that myopodin methylation was significantly associated with an increased recurrence rate (p=0.004), progression (p=0.002), and shorter disease-specific overall survival (p=0.020). Interestingly, in a subset of cases treated with BCG, myopodin methylation was also related to an increased recurrence rate (p=0.011), progression (p=0.030), and a shorter disease-specific overall survival (p=0.028). CONCLUSIONS: Epigenetic analyses revealed that myopodin methylation was associated with the clinical outcome of patients with T1G3 tumors. Myopodin methylation was related to tumor aggressiveness in patients with T1G3 disease undergoing BCG treatment. Myopodin methylation distinguished patients responding to BCG from those who may require a more aggressive therapeutic approach. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4673.