ESTRO 2024 - Abstract Book

S2223

Clinical - Upper GI

ESTRO 2024

2082

Digital Poster

Liver toxicity following SBRT: independent test of HyTEC recommendations

Vitali Moiseenko, Austin Hopper, Greg White, Jona Hattangadi-Gluth, Casey Bojechko

University of California San Diego, Radiation Medicine and Applied Sciences, La Jolla, USA

Purpose/Objective:

To evaluate if normal liver-sparing constraint recommendations from HyTEC comply with clinical experience. Also, to analyze liver toxicity data for association with dose-volume and patient-specific parameters.

Material/Methods:

Treatment planning and liver toxicity data were collected for 33 patients treated with gated liver SBRT, 12 diagnosed with primary liver cancer, and 21 with liver metastases. All patients were scanned with a 4D-CT, and gating was selected according to motion amplitude and whether a patient had fiducial markers implanted. SBRT plans were optimized to comply with HyTEC recommendations (1), with mean liver dose (MLD) <13 Gy for primary liver cancer and <15 Gy for metastatic lesions. A soft constraint to keep the maximum dose to spared 700 cc of normal liver, defined as liver minus ITV, below 15 Gy was used. If this was not achievable, then MLD took priority. The prescribed dose ranged from 25 to 60 Gy in 3-5 fractions. Acute and late toxicities evaluated include changes in lab values, symptomatic effects, and changes in Child-Pugh score. Changes from the pre-treatment baseline in liver function or blood counts within three months of SBRT were assessed according to CTCAE v5 (anemia, LFTs) or v3 (leukopenia/platelets). Any occurrence of pain, nausea/vomiting, cholangitis, biliary obstruction, fistula, GI bleeding, or liver failure was recorded and scored by CTCAE v5. Child-Pugh score was calculated at baseline, highest score at 3m post-treatment and at 12m and evaluated for decline. MLD, dose-volume values, and maximum dose to spared 700 cc of normal liver (D700cc), were extracted from treatment plans to test for correlation with toxicity. The MLD constraint was fulfilled for all patients; mean MLD was 7.1Gy, ranging from 1.98 to 12.4 Gy. Three patients developed grade 3+ liver enzyme toxicityand due to low incidence, further analysis was not possible. Mean liver D700cc was 5.1 Gy, ranging from 0.22 to 25.1 Gy. This constraint was not fulfilled for three patients, with D700cc 16.8, 18.1, and 25.1 Gy. Four patients developed grade 3 symptomatic liver toxicity, two developed grade 4, and one developed grade 5. Three of these seven patients were diagnosed with primary liver cancer, four with liver metastases. Child-Pugh class change with at least a 2-point increment was seen in five patients. No correlation with dose volume or maximum dose to spared 700 cc was observed for the studied cohort. Of note, the patient whose D700cc was 25.1 Gy developed grade 2 liver enzyme toxicity, grade 3 liver toxicity, and Child-Pugh class progression from B to C. Normal liver volume was smaller among patients who developed grade 3+ liver toxicity. This volume was <1200 cc in six of seven patients, compared to 12 in 26 patients who did not show high-grade toxicity. Three of seven patients had concurrent radiotherapy to the abdomen, e.g., pancreas, or prior radiotherapy to the abdominal Results: