An evaluation of the real world use and clinical utility of the Cxbladder Monitor assay in the follow-up of patients previously treated for bladder cancer

Abstract

Background: Surveilling recurrent urothelial carcinoma (UC) requires frequent cystoscopy, which is invasive, expensive and time-consuming. An accurate urinary biomarker has the potential to reduce the number of cystoscopies required during post-treatment surveillance. Objective: To audit the clinical utility of a new surveillance protocol incorporating the Cxbladder Monitor (CxbM) test in real-world practice. Methods: Three hospitals implemented a new surveillance protocol. Patients were risk stratified, and then provided urine samples for CxbM testing. Low-risk CxbM-positive patients and all high-risk patients had cystoscopy at 2-3 months. Low-risk CxbM-negative patients had cystoscopy at ~ 12 months. Results: 443 CxbM tests were conducted on samples from 309 patients: 257 (83.2%) low-risk and 52 (16.8%) high-risk. No pathology-confirmed recurrences were seen in low-risk CxbM-negative patients (n = 108) during the first post-CxbM cystoscopy undertaken a mean ± SD 10.3 ± 3.9 months after testing. Three recurrences were detected during cystoscopy at 2.7 ± 3.4 months in 53 low-risk CxbM-positive patients. In 49 high-risk patients, 39 (79.6%) were CxbM-negative with no pathology-confirmed recurrences. Ten high-risk patients (20.4%) were CxbM-positive with four confirmed recurrences; 2 high-grade and 2 low-grade. The median time to first cystoscopy was 12.13 (95% CI: 11.97-12.4) months in patients with a CxbM-negative result versus 1.63 (95% CI: 1.13-2.3) months in patients with a CxbM-positive result (p < 0.00001). No positive cases were missed, no patients progressed to invasive or metastatic disease, and no patient died of cancer over 35 months of follow-up. Conclusions: CxbM accurately identified a high proportion of patients (77.8%) who were safely managed with only one cystoscopy per year. Including CxbM in the protocol for patient surveillance provided clinical utility by reducing the average number of annual cystoscopies by approximately 39%, thereby sparing patients the potential discomfort and anxiety, without compromising detection rates. No advantage was observed for risk stratification prior to CxbM.