Impact of contouring methods on pre-treatment and post-treatment dosimetry for the prediction of tumor control and survival in HCC patients treated with selective internal radiation therapy

Abstract

Introduction The aim of this study was to evaluate the impact of the contouring methods on dose metrics and their predictive value on tumor control and survival, in both situations of pre-treatment and post-treatment dosimetry, for patients with advanced HCC treated with SIRT. Methods Forty-eight patients who underwent SIRT between 2012 and 2020 were retrospectively included in this study. Target volumes were delineated using two methods: MRI-based contours manually drawn by a radiologist and then registered on SPECT/CT and PET/CT via deformable registration (Pre-CMRI and Post-CMRI), 99mTc-MAA-SPECT and 90Y-microspheres-PET 10% threshold contouring (Pre-CSPECT and Post-CPET). The mean absorbed dose (Dm) and the minimal absorbed dose delivered to 70% of the tumor volume (D70) were evaluated with both contouring methods; the tumor-to-normal liver uptake ratio (TNR) was evaluated with MRI-based contours only. Tumor response was assessed using the mRECIST criteria on the follow-up MRIs. Results No significant differences were found for Dm and TNR between pre- and post-treatment. TNR evaluated with radiologic contours (Pre-CMRI and Post-CMRI) were predictive of tumor control at 6 months on pre- and post-treatment dosimetry (OR 5.9 and 7.1, respectively; p = 0.02 and 0.01). All dose metrics determined with both methods were predictive of overall survival (OS) on pre-treatment dosimetry, but only Dm with MRI-based contours was predictive of OS on post-treatment images with a median of 23 months for patients with a supramedian Dm versus 14 months for the others (p = 0.04). Conclusion In advanced HCC treated with SIRT, Dm and TNR determined with radiologic contours were predictive of tumor control and OS. This study shows that a rigorous clinical workflow (radiologic contours + registration on scintigraphic images) is feasible and should be prospectively considered for improving therapeutic strategy.

How the Rigid and Deformable Image Registration Approaches Affect the Absorbed Dose Estimation Using Images Collected before and after Transarterial Radioembolization with 90Y Resin Microspheres in a Clinical Setting

“…Specifically concerning 90 Y-loaded resin microspheres, a threshold of 100-120 Gy as a predictor of treatment response or OS has been identified by several studies [27]. In this context, therefore, the cutoff reported in the cohort of patients investigated in this study was in agreement with other authors [7,[28][29][30].…”

“…Moreover, Nodari et al [7] reported a cutoff in terms of the target mean absorbed dose of 115 and 98 Gy, using 99m Tc-MAA SPECT/CT-and 90 Y PET/CT-based dosimetry, respectively, for predicting the OS.…”

“…Unfortunately, the manual delineation of VOIs is time-consuming and might affect the accuracy of the volume, shape and position of the target and organs at risk (OARs), due to the inter-operator delineation variability on a given image [7]. This has been previously shown in TARE, where the variability between different readers led to tumor-absorbed doses with a low intra-class correlation coefficient (ICC), while showing higher ICC values for liver-absorbed doses [8].…”

Segmentation-guided multi-modal registration of liver images for dose estimation in SIRT

“…Nodari et al . used a multi-modality deformable registration algorithm in MIM SurePlan (v7.0.1; MIM software Cleveland, USA), performed by a trained medical physicist, to register the liver tumor contours from MR images to 99m Tc-MAA-SPECT/CT and 90 Y-PET/CT [ 19 ]. Their study indicates that different tumor contours from anatomical and scintigraphic images have no significant impact on mean dose, and registering anatomical tumor contours to scintigraphic images is feasible for improving therapeutic strategy [ 19 ].…”

“…used a multi-modality deformable registration algorithm in MIM SurePlan (v7.0.1; MIM software Cleveland, USA), performed by a trained medical physicist, to register the liver tumor contours from MR images to 99m Tc-MAA-SPECT/CT and 90 Y-PET/CT [ 19 ]. Their study indicates that different tumor contours from anatomical and scintigraphic images have no significant impact on mean dose, and registering anatomical tumor contours to scintigraphic images is feasible for improving therapeutic strategy [ 19 ]. Besides, our in-house non-rigid liver registration regularized by a spring model was applied in our previous studies on the development of pre-treatment dosimetry [ 6 ] and evaluation of the predictive value of 99m Tc-MAA-based dose planning [ 20 ].…”