Abstract 2127: TERT C228T and KDM6A alterations are potential predictive biomarkers in non-muscle-invasive bladder cancer treated with intravesical Bacillus Calmette-Guérin instillation

Introduction: Bacillus Calmette-Guérin (BCG) is the standard of care for high-risk non-muscle-invasive bladder cancer (NMIBC) following transurethral resection. However, patients often have heterogeneous responses. Even among those who initially respond well to BCG, 10-20% relapse. Identification of reliable biomarkers predicting the efficacy of BCG remains an unmet need. En bloc resection is a novel technique representing a substantial advancement in the surgical management of NMIBC. We sought to investigate genomic and tumor microenvironmental (TME) profiles in NMIBC and explore potential predictive markers for BCG treatment following en-block resection. Methods: A total of 40 patients with high-risk NMIBC (cTis-T1N0M0) were retrospectively enrolled who underwent en bloc resection followed by BCG instillation. Surgical samples were subjected to NGS sequencing using a 520-gene panel (Burning Rock Biotech, Guangzhou) and multiplex immunofluorescence (mIF) assay. Results: The cohort had a median age of 63 years, and 80% were male. After a median follow-up of 21.8 months, 19/40 patients relapsed with a one-year relapse-free survival (RFS) rate of 57.5%. All tumors were microsatellite stable and showed a median TMB of 7.98muts/Mb. Genomic profiling revealed a high prevalence of alterations in TERT (55%), KDM6A (32.5%), KMT2D (32.5%), FGFR3(30%), PIK3CA (30%), TP53(27.5%), KMT2C (25%), and ARID1A (20%). TME analysis showed higher proportions of M1 macrophages and CD56 dim NK cells in the tumoral compartment and more intense infiltration of CD8+ T cells, exhausted CD8+T, CD56 bright NK cells, and M2 macrophages in the stromal compartment. Multivariate analysis identified TERT C228T mutation (HR=3.28 [95%CI:1.225-8.79], p=0.0181) and alteration in KDM6A (HR=2.94 [95%CI:1.040-8.29], p=0.042) as two independent factors associated with inferior RFS. Patients with concomitant TERT C228T and KDM6A alteration had the shortest RFS (median RFS:5.83months) compared with those who were free of (median RFS: NR) or harbored either one of the two alterations (median RFS:9.13months) (p=0.0022). We also found that tumoral infiltration of CD8+T cells was positively associated with RFS (HR=0.29 [95%CI:0.097-0.885], p=0.0208). Conclusion: The study comprehensively depicted the genomic and TME profiles in NMIBC and identified potential predictive biomarkers for BCG treatment. Our findings may facilitate the stratification of patients and better guide the clinical decision-making on the management of NMIBC. Citation Format: Qi-Dong Xia, Yao-Bing Chen, Jian-Xuan Sun, Chen-Qian Liu, Jin-Zhou Xu, Zhi-Peng Yao, Ye An, Meng-Yao Xu, Si-Han Zhang, Xing-Yu Zhong, Na Zeng, Si-Yang Ma, Hao-Dong He, Heng-Long Hu, Jia Hu, Yi Lu, Lin Shao, Si-Qi Li, Zheng Liu, Shao-Gang Wang. TERT C228T and KDM6A alterations are potential predictive biomarkers in non-muscle-invasive bladder cancer treated with intravesical Bacillus Calmette-Guérin instillation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2127.