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-C_MRI and Post-C_MRI), ^99mTc-MAA-SPECT and ⁹⁰Y-microspheres-PET 10% threshold contouring (Pre-C_SPECT and Post-C_PET). 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-C_MRI and Post-C_MRI) 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.

Keywords: Dosimetry; Hepatocellular carcinoma; Radioembolization.

Fig. 1

Example of dose volume histogram (DVH) computed with MiM Sureplan 7.0.1 software research workflow on pre-treatment ^99mTc-MAA SPECT/CT images. Abscissa is the minimal absorbed dose; ordinate is the corresponding relative volume receiving the absorbed dose. Green curve represents the liver contour; blue curve represents Pre-C_MRI tumor contour; red curve represents Pre-C_SPECT 10% threshold target contour

Fig. 2

Illustration of two patients with MRI on the top (a and b) and tumors outlined in dark blue then registered on ^99mTc-MAA SPECT/CT and ⁹⁰Y-microspheres PET/CT via deformable registration. Yellow and light blue contours correspond to SPECT/CT and PET/CT 10% thresholds contours, respectively. First patient (a, c and e) had a very high TNR determined with MRI-based contours: 10 on SPECT/CT and 19 on PET/CT. Second patient (b, d and f) had a very low TNR: 4 on SPECT/CT and 3 on PET/CT. In those cases, for example first patient with a very high TNR had a tumor control during 38 months and second patient with a very low TNR had a tumor control during 2 months

Fig. 3

Boxplots of dose metrics based on imaging before SIRT (^99mTc-MAA SPECT/CT; pre-treatment dose metrics) and after SIRT (⁹⁰Y-microspheres PET/CT; post-treatment dose metrics) in patients receiving resin microspheres

Fig. 4

Boxplots of dose metrics based on imaging before SIRT (^99mTc-MAA SPECT/CT; pre-treatment dose metrics) and after SIRT (⁹⁰Y-microspheres PET/CT; post-treatment dose metrics) in patients receiving glass microspheres

Fig. 5

Kaplan–Meier curves on overall survival according to inframedian (blue curve) or supramedian (green curve) Dm, D70 and TNR