Cervical cancer outcome prediction to high-dose rate brachytherapy using quantitative magnetic resonance imaging analysis of tumor response to external beam radiotherapy

Abstract Background and purpose In order to assess tumor regression and outcomes, a volumetric analysis was conducted for cervical cancer patients treated with magnetic resonance imaging (MRI)-based image-guided brachytherapy (IGBT). Materials and methods Consecutive patients with FIGO stage IB1–IVA cervical cancer receiving chemoradiation from 2007 to 2013 were identified, excluding patients with perineal template-based interstitial brachytherapy or without undergoing MRI. A ring and tandem applicator ± interstitial needles was used. T2-weighted imaging was completed following applicator insertion. Gross tumor volumes (GTVs) were retrospectively contoured: initial GTV (GTVPre-EBRT ), GTV at first brachytherapy (GTVIGBT ) and percent residual GTV at first brachytherapy (% GTVResidual ). Results Eighty-four patients were identified. With 20.8-month median follow-up, two-year estimates of local control (LC), disease-free survival (DFS) and overall survival (OS) were 91.3, 79.8, and 85.0%, respectively. Multivariate Cox regression revealed adenocarcinoma (HR 5.88, p = 0.03) and GTVIGBT (HR 1.17, p < 0.01) as predictors for local failure. GTVIGBT > 7.5 cc was associated with inferior 2-year LC (75.0 vs. 96.6%, p < 0.01), DFS (42.6 vs. 91.6%, p < 0.01) and OS (65.2 vs. 91.5%, p < 0.01). No difference in mean HRCTV D90 EQD2 was seen between the groups ( p = 0.61). Conclusion Aside from known benefits of IGBT, MRI-based planning allows for assessment of tumor regression and prognosticates patients.