3579 - A Preliminary Investigation into the Clinical Application of Magnetic Resonance Linear Accelerator for Treating Hepatocellular Carcinoma and Colorectal Cancer Liver Metastasis
Presenter(s)
Y. Zong, K. Men, S. Wang, Y. Tang, S. Qin, Y. Liu, Y. Song, H. Jing, H. Fang, N. Lu, Z. Yang, and B. Chen; Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
Purpose/Objective(s): This study evaluated the efficacy and safety of magnetic resonance linear accelerator (MR-Linac) for treating patients with hepatocellular carcinoma (HCC) and colorectal cancer liver metastasis.
Materials/Methods: Patients with HCC or colorectal cancer liver metastasis who received stereotactic body radiation therapy (SBRT) on a MR-Linac from a precision radiation medicine company were identified at our institution. The prescription doses were 40-48 Gy for planning target volume (PTV) and 48-55 Gy for the gross tumor volume (GTV) for HCC. The prescription doses were 30-50 Gy for PTV and 40-60 Gy for GTV for colorectal cancer liver metastasis. The number of fractions were 5, 9 or 10. Patients received SBRT in 5 fractions when the GTV was far away from gastrointestinal (GI) tract, and 10 fractions when close to GI tract. The definition of the recognition rate was the percentage of the patients with GTVs clearly displayed in MR images for alignment. After SBRT, patients were followed up at 1, 3, 6 and 12 months, and 3 to 6 months thereafter. The in-field objective response rate (ORR), ORR, local progression free survival (LPFS), PFS, overall survival (OS) and toxicity were recorded.
Results: Forty-one patients (15 HCC and 26 colorectal cancer liver metastases) with 54 lesions were retrospectively enrolled between November 2019 and August 2023. The recognition rate was 87.8% (36/41 patients). The presence of blood vessels and bile ducts adjacent to the GTV assisted with the precise alignment for the remaining patients. According to Response Evaluation Criteria in Solid Tumors, version 1.1, the in-field ORR were 39% and 68.3% at 1 and 3-6 months after SBRT, respectively. Patients with HCC had a significant higher in-filed ORR compared with those with liver metastases (93.3% vs 53.8%, P = 0.023) at 3-6 months after SBRT. The most common site of first failure was the out-of-filed liver (6/41 patients,14.6%), the in-filed liver (3/41 patients, 7.3%), followed by the lungs (2/41 patients, 4.9%) within 3-6 months after SBRT. The median follow-up was 36.9 months. The 2-year LPFS rate was 69.3%. The 2-year LPFS rates were 90% vs 56.2% for HCC versus liver metastasis (P = 0.021). The median PFS was 15.9 months (95% confidence interval [CI], 7.8-24.0). The median PFS were 38.2 months (95% CI, 25.8-50.6) versus 8.9 months (95% CI, 5.0-12.8) for HCC versus liver metastasis (P = 0.005). The 2-year OS rate was 73.5%. The 2-year OS rates were 93.3% versus 60% for two groups (P = 0.032). Toxicities were mild and no grade 3 or higher toxicities were observed.
Conclusion: MR-Linac provides a platform with a high recognition rate of intrahepatic lesions. The optimal time for treatment response is 3-6 months after SBRT. MRI-guided radiotherapy is a noninvasive and well-tolerated treatment with excellent local control for liver malignancies.