Lesion Volume Divided by ADC Measures Is an Independent Prognostic Marker in Colorectal Liver Metastasis Treated by Y90-radioembolization.

Background/aim: To assess the ability of apparent diffusion coefficient (ADC) at baseline in predicting overall survival in patients who undergo Y90-radioembolization (Y90-RE) for liver-dominant metastatic colorectal cancer (mCRC) in the salvage situation.

Patients and methods: A retrospective review of 411 lesions in 63 patients with refractory mCRC treated with Y90-RE was conducted. Manual region of interest (ROI) measurements were applied using a whole lesion and volume method. Minimum and mean ADC values were measured, and averages were calculated per patient. Ratios combining tumor volume and ADC were correlated with OS, and a receiver-operating characteristic (ROC) analysis defined a cut-off value. Cox regression analysis was performed, and the log-rank test confirmed prognostic cut-off levels for survival.

Results: The median survival was 6.4 months. Multivariate Cox regression identified tumor volume divided by minimum ADC (ADC_{tumor volume, min}) as an independent predictor of OS (HR=1.814, 95%CI=1.188-2.770, p=0.006). Neither ADCmin nor ADCmean were significantly associated with survival. Optimal prediction was identified with a ADC_{tumor volume, min} cut-off of 0.3673 arbitrary units (AU) yielding 76.0% sensitivity and 70.3% specificity. Patients with ADC_{tumor volume min} <0.3673 had a median OS of 10.4 months, compared to 4.7 months for those above the cut-off (p<0.001).

Conclusion: Tumor volume divided by minimum ADC at baseline (ADC_{tumor volume, min}) was identified as an independent predictor of OS in mCRC scheduled for Y90-radioembolization in the salvage situation and may improve future patient selection.