2184 - Association of Liver Elastography and Clinical Outcomes Among Patients with Hepatocellular Carcinoma Treated with Definitive External Beam Radiation Therapy

03:00pm - 04:00pm ET

Poster Hall - Exhibit Hall A

Screen: 29

POSTER

Presenter(s)

Madhurya Reddy, MD, MBBS - Mayo Clinic, Rochester Radiation Oncology, Rochester, MN

M. Reddy¹, P. Karki¹, K. M. Pepin², S. Venkatesh³, R. Ehman³, M. G. Haddock¹, K. R. Jethwa¹, K. W. Merrell¹, C. M. Callaghan¹, Y. Sharifzadeh¹, E. J. Tryggestad¹, C. L. Hallemeier¹, and A. D. Sherry¹; ¹Department of Radiation Oncology, Mayo Clinic, Rochester, MN, ²Resoundant Inc., Rochester, MN, ³Department of Radiology, Mayo Clinic, Rochester, MN

Purpose/Objective(s): For definitive treatment of hepatocellular carcinoma (HCC) with external beam radiation therapy (EBRT), additional predictive factors are needed. Magnetic resonance elastography (MRE) is an in vivo imaging technique that measures tissue viscoelastic properties and can be integrated into the standard simulation process without substantial added scan time and cost to the patient. Building on our prior work (Mullikin TC et al, ADRO 2021), we investigated whether pre-EBRT 2D MRE-defined liver stiffness (LS) predicts outcomes after definitive EBRT for HCC.

Materials/Methods: After IRB approval, we performed a retrospective cohort study of adults with non-metastatic HCC who underwent pre-EBRT 2D MRE acquired using standard techniques as part of the treatment planning MRI before definitive EBRT. LS was averaged across four axial slices. Outcomes included progression-free survival (PFS) and overall survival (OS). Multivariable Cox regression evaluated associations between MRE and outcomes, adjusting for age, T stage, and CP status identified using a structural causal model with a directed acyclic graph. A sensitivity model additionally adjusted for mean liver-gross tumor volume (GTV) equivalent dose in 2-Gy fractions (EQD2) (a/ß = 3) to the aforementioned factors given the established relationship between uninvolved liver dose and outcomes.

Results: A total of 128 patients with a median follow-up of 32 months (IQR, 16-70) were identified. Of these, 110 patients (86%) were CP class A liver disease before EBRT and 19 (15%) had T4 staging. Photons were used to treat 65 patients (51%) and protons in 63 patients (49%). Among patients who received stereotactic body radiation therapy, 50 Gy in 5 fractions was the most common regimen, while 67.5 Gy in 15 fractions was the most common moderate hypofractionation approach. The median liver-GTV mean dose was 7 Gy (IQR, 4-12). Median PFS and OS were 12 and 19 months, respectively.

Independent of confounding factors, higher pre-EBRT LS was associated with shorter OS (HR, 1.19; 95% CI: 1.01 to 1.40; p = 0.04) and showed a trend toward shorter PFS (HR, 1.12; 95% CI: 0.99 to 1.27; p = 0.08). Adjusting for mean uninvolved liver dose yielded similar results for OS (HR, 1.20; 95% CI: 1.02 to 1.42; p = 0.03) and PFS (HR, 1.11; 95% CI: 0.97 to 1.26; p = 0.12).

Conclusion: Among patients with HCC receiving definitive EBRT, MRE-based LS may facilitate patient selection and prognostication by serving as an actionable non-invasive biomarker, supplementing traditional clinical factors. The results support further investigation of more advanced MRE acquisition methods and prospective evaluation of optimal integration into EBRT planning.