Image-Guided Hypofractionated Stereotactic Ablative Radiotherapy For The Liver: The Maastro Experience

Introduction: Stereotactive ablative body radiotherapy (SABR) is a non-invasive treatment option for inoperable patients or patients with irresectable liver oligometastases or primary hepatocellular carcinoma. Outcome and toxicity were evaluated retrospectively in this single-institution patient cohort.Methods: Between 2010-2014, 35 lesions in 31 consecutive patients (16 male, 15 female, median age 68 yrs) were irradiated. All lesions were liver metastases (n = 30) of various primary tumors (8 colon, 7 rectum, 5 breast, 2 stomach, 1 ovarium, 1 anal canal, 1 renal cell carcinoma, 1 endometrial stroma cell carcinoma) or primary hepatocellular carcinomas (n = 5). Patients were considered to be technically or medically inoperable by an interdisciplinary tumor board. Consequently, the population is characterized with frailty and overall poor prognosis. We analysed local control (LC) with focus on CT-based response at three-month, 1-year, two-year overall survival (OS) and progression pattern.Results: Of all patients only 22.6% (n = 7) had extrahepatic disease at the start of SABR. All patients were treated with hypofractionated image-guided stereotactic radiotherapy. EQD2 (equivalent dose in 2 Gy fractions) varied from 62.5 Gy to 150 Gy delivered in 3 to 10 fractions (median dose 93.8 Gy, alpha/beta =10). CT-based regression pattern three months after radiotherapy revealed regression in 70.9% of patients with a complete remission in 29% of the cases. The site of first progression was predominantly distant. In 19.5% of patients the progression pattern was distant only and in an equal percentage the pattern was distant and outfield hepatogenous. Only one patient developed progressive disease in the radiation field as well as a lung metastasis. About 41.9% patients remained free from progression at last follow-up (median follow-up is 21 months). 1-Year and 2-year overall survival is 87% and 81% respectively. Regarding dose-treatment effect, we recorded a significantly higher rate of complete and partial remission with an EQD2 >100Gy (p value = 0.021). Furthermore, PTV was significantly lower for patients with complete or partial remission (average volume 133 vs 277cc respectively, p = 0.026). ). No acute toxicity of grade 2 or higher was observed.Conclusion: SABR liver offers a safe and efficient treatment strategy for selected inoperable patients or irresectable tumours of the liver. Despite the small population we observed a trend to higher local control with a higher EQD2. Our margin recipe seems adequate but the main issue is out of field relapses. In future studies we should combine SABR with systemic treatment acting in synergy with radiation such as immunological interventions. Introduction: Stereotactive ablative body radiotherapy (SABR) is a non-invasive treatment option for inoperable patients or patients with irresectable liver oligometastases or primary hepatocellular carcinoma. Outcome and toxicity were evaluated retrospectively in this single-institution patient cohort. Methods: Between 2010-2014, 35 lesions in 31 consecutive patients (16 male, 15 female, median age 68 yrs) were irradiated. All lesions were liver metastases (n = 30) of various primary tumors (8 colon, 7 rectum, 5 breast, 2 stomach, 1 ovarium, 1 anal canal, 1 renal cell carcinoma, 1 endometrial stroma cell carcinoma) or primary hepatocellular carcinomas (n = 5). Patients were considered to be technically or medically inoperable by an interdisciplinary tumor board. Consequently, the population is characterized with frailty and overall poor prognosis. We analysed local control (LC) with focus on CT-based response at three-month, 1-year, two-year overall survival (OS) and progression pattern. Results: Of all patients only 22.6% (n = 7) had extrahepatic disease at the start of SABR. All patients were treated with hypofractionated image-guided stereotactic radiotherapy. EQD2 (equivalent dose in 2 Gy fractions) varied from 62.5 Gy to 150 Gy delivered in 3 to 10 fractions (median dose 93.8 Gy, alpha/beta =10). CT-based regression pattern three months after radiotherapy revealed regression in 70.9% of patients with a complete remission in 29% of the cases. The site of first progression was predominantly distant. In 19.5% of patients the progression pattern was distant only and in an equal percentage the pattern was distant and outfield hepatogenous. Only one patient developed progressive disease in the radiation field as well as a lung metastasis. About 41.9% patients remained free from progression at last follow-up (median follow-up is 21 months). 1-Year and 2-year overall survival is 87% and 81% respectively. Regarding dose-treatment effect, we recorded a significantly higher rate of complete and partial remission with an EQD2 >100Gy (p value = 0.021). Furthermore, PTV was significantly lower for patients with complete or partial remission (average volume 133 vs 277cc respectively, p = 0.026). ). No acute toxicity of grade 2 or higher was observed. Conclusion: SABR liver offers a safe and efficient treatment strategy for selected inoperable patients or irresectable tumours of the liver. Despite the small population we observed a trend to higher local control with a higher EQD2. Our margin recipe seems adequate but the main issue is out of field relapses. In future studies we should combine SABR with systemic treatment acting in synergy with radiation such as immunological interventions.