Evaluation of early response to neoadjuvant chemotherapy in muscle-invasive bladder cancer using dynamic contrast-enhanced MRI and diffusion weighted MRI: MARBLE study.

403 Background: Functional imaging techniques which evaluate early treatment responses may identify non-responders who would benefit from a switch in therapy. This is a prospective feasibility study of serial diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) MRI scanning in patients undergoing neoadjuvant chemotherapy for muscle-invasive bladder cancer. Methods: Scans were performed before and during chemotherapy (10-17 days after the first and second cycles). A repeatability DW-MRI scan was acquired on the first visit. Regions-of-interest (ROI) encompassing the entire tumour were defined. Analysis of MRI parameters was undertaken and related to findings from the routine restaging CT scan performed after 3 cycles of chemotherapy. Results: 10/16 patients were male, median age 59 years, 14/16 had T3/4 disease, and 5/16 were node positive. 10/16 have completed 3 or 4 cycles of chemotherapy to date and attended for the restaging CT scan. Radiological response was identified in all cases. In the DW-MRI analysis there was no significant difference in mean tumour ADC or tumour volume between baseline and repeatability scans (mean ADC 1.19 and 1.2 respectively, n=16). Visual assessment showed a fall in contrast agent uptake within the primary bladder tumour after treatment. Conclusions: The scanning protocols enabled visualisation of the bladder tumours and derivation of kinetic parameters. DW-MRI measurements were comparable between baseline and repeat scan, suggesting that a change in ADC was more likely to be attributable to treatment response or disease progression than measurement error or inherent variation. Statistically significant rises in mean ADC and decreases in tumour volume were observed early in the treatment pathway. No patients progressed on treatment in this study. Larger studies of DCE and DW-MRI as surrogate response imaging biomarkers in bladder cancer are recommended. Clinical trial information: Study ID 14489. [Table: see text]