Development and psychometric evaluation of a patient-reported symptom index for patients with non-muscle invasive bladder cancer: the NMIBC-SI

Background and objective: Non-muscle invasive bladder cancer (NMIBC) is a chronic condition requiring frequent follow-up with endoscopic examinations, tumour resections and intravesical treatments. In this clinical context, patient-reported outcomes (PROs) have enormous potential to inform treatment assessment and recommendations for NMIBC. We aimed to develop and evaluate a patient-reported NMIBC Symptom Index (NMIBC-SI) to facilitate clinical research and enhance care. Methods: NMIBC-SI items were developed based on existing literature and qualitative interviews with patients and clinicians, and evaluated in two field tests: item reduction, using NMIBC-SI data from 220 patients on active treatment from nine Australian centres; reliability and validity evaluation of item-reduced version using NMIBC-SI data from 232 patients from five countries. Results: NMIBC-SI assesses disease and treatment-related symptom burden and two treatment-specific side-effects (cystoscopy, intravesical BCG/Chemotherapy). Composite analysis supported a single composite model including core symptom and cystoscopy index items (Intravesical index items were not tested due to small sample). Test-retest reliability was strong (range 0.894–0.91). As expected, the NMIBC-SI was able to discriminate between no treatment and any treatment groups, and no treatment and chemo/BCG groups, providing evidence towards validity. Conclusions and clinical implications: NMIBC-SI assesses patients’ self-reported symptom burden and can be used to evaluate NMIBC treatments from the perspective of patients. The NMIBC-SI is acceptable to patients and has evidence for reliability and validity. Future validation work with patients with greater symptom burden is warranted.