Surveillance of non-muscle invasive bladder cancer (NMIBC) is essential for patients with a history of urothelial carcinoma (UC), but bothersome due to the frequent need for cystoscopy. Cxbladder Monitor is a non-invasive diagnostic test that screens for 5 UC biomarkers plus clinical factors to monitor patients with a history of UC for disease recurrence. The LOBSTER study aims to validate the diagnostic performance of Monitor and Cxbladder Monitor Plus (its second-generation test) for NMIBC surveillance. The primary objective of these assays is refinement of clinical pathways to enable cystoscopy deferral for Monitor Plus-negative patients and prioritize immediate evaluation for Monitor Plus-positive patients. Correlative tumor genotyping using DNA markers is included to enhance understanding of UC risk.

LOBSTER is a prospective, multicenter, observational study that plans to enroll up to 700 patients across diverse medical centers, including Veterans Affairs facilities, with a target of 75 patients with a pathologically confirmed NIMBC recurrence. Eligible patients are undergoing NMIBC surveillance, and stratified into low-, intermediate-, or high-risk groups based on 2025 American Urological Association microhematuria guidelines. Patients provide voided urine sample(s) during initial and subsequent surveillance cystoscopy visits over a 2-year follow-up period, to be analyzed using Monitor, Monitor Plus, and by central urine cytology. Additionally, DNA genotyping will be conducted using primary tumor tissues, when available, or any tissue from recurrences during the study to correlate genetic markers with UC recurrence risk. The study design is blinded, with clinicians and patients being unaware of test results. Consecutive patient recruitment ensures a representative NMIBC population. Baseline demographic data will be analyzed descriptively. The primary endpoints are sensitivity, specificity, positive predictive value, negative predictive value, and test-negative rates of the Cxbladder tests compared with pathology (gold standard), each reported with corresponding 95% confidence intervals. Secondary endpoints explore clinical utility in stratified risk groups.

Currently, 423 patients are enrolled including 52 patients with NMIBC recurrence. Recruitment will continue until 75 patients are confirmed with a recurrence. This will trigger an interim analysis projected for Dec-25.

The results of the LOBSTER study will help to confirm the clinical validity of Cxbladder Monitor and Cxbladder Monitor Plus, which may aid clinicians in the risk stratification of patients who are undergoing surveillance for recurrent UC.