Abstract 547: Urine tumor DNA MRD detection and correlation with pathologic complete response in muscle-invasive bladder cancer treated with curative-intent radical cystectomy

Objective: Standard-of-care for muscle-invasive bladder cancer (MIBC) is neoadjuvant chemotherapy followed by radical cystectomy. The inability to assess molecular residual disease (MRD) noninvasively limits our ability to offer bladder-sparing treatment. We seek to develop a liquid biopsy solution via urine tumor DNA (utDNA) analysis. Methods: We applied uCAPP-Seq, a targeted next-generation sequencing method for detecting utDNA, to urine cell-free DNA samples acquired on the day of curative-intent radical cystectomy from 42 patients with non-metastatic bladder cancer, 30 of whom had a confirmed diagnosis of MIBC and 19 of whom received neoadjuvant chemotherapy. utDNA mutational calling was performed noninvasively without tumor tissue sequencing knowledge. The overall utDNA level for each patient was represented by the non-silent mutation with the highest duplex-supported variant allele fraction after removing germline variants. Urine was similarly analyzed from 15 healthy donors. The concordance between urine cell-free DNA and tumor tissue was determined for a subset of patients. Tumor mutational burden (TMB) in utDNA MRD-positive patients was inferred from the number of mutations detected in urine cell-free DNA by applying a linear relationship derived from TCGA whole-exome sequencing of 409 MIBC tumors. Results: utDNA analysis revealed a median utDNA level of 0% in healthy donors and 2.4% in non-metastatic bladder cancer patients. Concordance between urine- and tumor-derived mutations, determined in 5 MIBC patients, was 87%. When patients were classified as those who had residual disease detected in their surgical sample (n = 16) compared to those who achieved a pathologic complete response (n = 26), median utDNA levels were 4.3% vs. 0%, respectively (P = 0.002). The lack of utDNA MRD detection was highly correlated with pathologic complete response by Fisher9s exact test (P = 0.0001) with Youden9s index-determined sensitivity of 81% and specificity of 81%. Moreover, utDNA MRD-positive patients exhibited significantly worse progression-free survival compared to utDNA MRD-negative patients (HR = 7.2; P = 0.03) with a median follow-up time of 200 days. Leveraging data from TCGA, the median inferred TMB in utDNA MRD-positive patients was 198 mutations per exome. We suggest that 58% of these patients with inferred TMB ≥ this level might have been candidates for early immune checkpoint blockade. Conclusion: The lack of utDNA MRD detection prior to curative-intent radical cystectomy for muscle-invasive bladder cancer correlated significantly with pathologic complete response. utDNA MRD detection status also correlated significantly with progression-free survival. Furthermore, utDNA results can be used to noninvasively infer TMB, which may facilitate the targeted use of adjuvant immunotherapy. Citation Format: Kevin Chen, Pradeep S. Chauhan, Ramandeep K. Babbra, Wenjia Feng, Peter K. Harris, Katherine Dienstbach, Andrew Atkocius, Lenon Maguire, Faridi Qaium, Armaan Nallicheri, Brian C. Baumann, Melissa A. Reimers, Eric H. Kim, Zachary L. Smith, Vivek K. Arora, Aadel A. Chaudhuri. Urine tumor DNA MRD detection and correlation with pathologic complete response in muscle-invasive bladder cancer treated with curative-intent radical cystectomy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 547.