Initial experience of dynamic contrast enhance magnetic resonance imaging (DCE-MRI) to assess therapeutic response to neoadjuvant chemotherapy and radical radiotherapy in bladder preservation for muscle invasive bladder cancer (MIBC)
Session type: Poster / e-Poster / Silent Theatre session
Response assessment to radical treatment is essential for bladder preservation in MIBC. DCE-MRI has been shown to discriminate between residual tumour and post-treatment change after neoadjuvant chemotherapy in MIBC using parameters such as relative signal intensity at 80s (RSI80s), and tracer kinetic parameters, particularly perfusion (Fp). This study assesses whether these parameters correlate with cystoscopic response to neoadjuvant chemotherapy followed by radical radiotherapy in MIBC.
Eleven patients with T2-4aN0M0 MIBC who received 3 cycles of gemcitabine/cisplatin neoadjuvant chemotherapy followed by radical radiotherapy (52.5Gy in 20 fractions over 4 weeks) underwent DCE-MRI at 3 time points: pre-treatment, after neoadjuvant chemotherapy and after radiotherapy. Each patient received intravenous Magnevist 0.1mmol/kg . An axial T1-w VIBE sequence covering the bladder was used for dynamic acquisitions (temporal resolution, 2.5 s). Volumes-of-interest (VOIs) were defined around suspicious areas using high resolution T2-w scans and transferred to dynamic scans. Whole VOI signal-time curves were analysed to obtain estimates of Fp and RSI80s. Changes in parameters between scans were calculated using paired student t-test and correlated with cystoscopy/biopsy results.
All eleven patients had allthree scans and subsequent cystoscopy/biopsy. The mean Fp pre-treatment (0.34ml/ml/min) for all patients reduced after neoadjuvant chemotherapy (0.19ml/ml/min,p=0.049) and further decreased after radiotherapy (0.13ml/ml/min,p=0.054). 9 patients had complete response at cystoscopy/biopsy and their mean Fp pre-treatment (0.36ml/ml/min) decreased after chemotherapy (0.21ml/ml/min,p=0.104) and again decreased after radiotherapy (0.12ml/ml/min,p=0.068). In 2 patients with residual disease, mean Fp decreased post-chemotherapy (0.38 to 0.12ml/ml/min,p=0.263) but both patients' Fp values increased post-radiotherapy (mean 0.21ml/ml/min,p=0.363). RSI80s values showed a similar but less consistent trend.
DCE-MRI offers the promise of earlier tumour response assessment after neoadjuvant chemotherapy and radiotherapy compared to conventional MRI. This could improve informed decision making for patients opting for bladder preservation and allow adaptive optimisation of radiotherapy or consideration of early salvage cystectomy.