Pre-Brachytherapy Diffusion-Weighted Magnetic Resonance Imaging (DW-MRI) Response as Predictor of Local Control in the Definitive Treatment of Cervical Cancer

PURPOSE/OBJECTIVE(S)

Chemoradiation consisting of external beam radiotherapy (EBRT) followed by brachytherapy (BT) is the standard of care for Stage IB2-IVA cervical cancer (CC). Multi-parametric MRI (mpMRI) is a valuable tool for initial staging, treatment planning and response assessment. In this study, we aim to explore the potential of mpMRI, in particular DW-MRI, to predict overall tumor control following chemoradiation in CC.

MATERIALS/METHODS

We identified 78 consecutive patients treated with chemoradiation for FIGO IB2-IVA CC between 2012-2020, who had an MRI at baseline (MRb) and post-EBRT prior to brachytherapy boost (MRpb) that included DW-MRI (b-value = 0 and 800 s/mm2). Median age was 53 years, most patients had squamous cell carcinoma (76.9%) and advanced-stage disease (56.4% stage IIIA-IVA). Median time from completion of EBRT to MRpb was 3 days. Regions of interest (ROI) in primary tumor were delineated on DW image (b = 0 s/mm2) using ITK-SNAP software. DW-MRI data were fitted to a monoexponential model to calculate apparent diffusion coefficient (ADC) values using in-house software platform (MRI-QAMPER). MRpb mean ADC values (n = 78) and relative changes (%) in mean ADC values between MRb and MRpb (n = 64) were correlated with outcomes, including local failure (LF), regional or distant failure (RDF), and failure at any site (FAS), with death without failure as a competing risk. Median follow-up time was 45 months (95% CI 38, 53).

RESULTS

At first post treatment assessment, 72 patients (92.3%) had a complete response (CR) in the cervix and 68 patients (87.2%) had CR in all disease sites. Of patients who had CR in the cervix (n = 72), only 1 patient had local recurrence. Of patients who had CR in all disease sites, 10 later recurred (1 LF only, 1 LF&RDF, 8 RDF only). Overall, 7 patients (9%) had LF, and 19 patients (24.4%) had FAS. A higher mean ADC value in MRpb was associated with LF (HR 4.3, 95% CI 1.32, 14.6; P = 0.016), but not with RDF (P = 0.4) or FAS (P = 0.5). A higher relative change in the mean ADC value between MRb and MRpb was associated with a lower risk of LF (HR 0.94, 95% CI 0.90, 0.98; P = 0.002), but not with RDF (P = 0.8) or FAS (P = 0.4).

CONCLUSION

Treatment response as measured on prebrachytherapy DW-MRI is a significant predictor of local control in patients undergoing chemoradiation for stage IB2-IVA CC. ADC values, a quantitative imaging biomarker on MRpb may be instrumental in dose intensification/de-escalation efforts in CC.