ESTRO 2023 - Abstract Book

S1085

Digital Posters

ESTRO 2023

Conclusion First exploration of MR-guided SBRT to pancreatic oligometastases of RCC indicates that it can be an effective and safe treatment option. Moreover, MR-guided SBRT may facilitate deferral of systemic therapy initiation in this select group of patients with favourable prognosis.

PO-1354 Pattern of failure after stereotactic body radiotherapy to liver metastases: impact of local control

A.G. Allegra 1 , M. Loi 1 , L. Angelini 1 , I. Bonaparte 1 , N. Bertini 1 , G. Frosini 1 , C. Orsatti 1 , M. Valzano 1 , P. Bonomo 1 , G. Simontacchi 1 , G. Francolini 1 , B. Detti 1 , V. Di Cataldo 1 , L. Visani 2 , V. Salvestrini 2 , L. Marrazzo 3 , M. Zani 3 , L. Masi 4 , R. Doro 4 , L. Livi 1 1 Azienda Ospedaliero Universitaria Careggi, Università di Firenze, Radiation Oncology, Florence, Italy; 2 Istituto Fiorentino di Cura e Assistenza (IFCA), CyberKnife Center, Florence, Italy; 3 Azienda Ospedaliero Universitaria Careggi, Università di Firenze, Medical Physics Unit, Florence, Italy; 4 Istituto Fiorentino di Cura e Assistenza (IFCA), Department of Medical Physics, Florence, Italy Purpose or Objective Surgical resection of liver metastases (LM) may be feasible for only 30% of patients due to unfavourable location, disease burden or comorbidities. There’s evidence of excellent local control (LC) and low toxicity in patients treated with stereotactic body radiotherapy (SBRT) but data on global disease control are scarce. The objective of this preliminary analysis was to assess patterns of failure in a cohort of patients treated with SBRT to LM. Materials and Methods Data from patients treated between 2018 and 2020 at a single Institution with SBRT to LM were collected. Patients received an EQD2 of at least 50 Gy ( α / β =10) as per ESTRO consensus. Failure patterns after SBRT defined as local relapse (LR), intrahepatic relapse (out of field, IHR) and extrahepatic relapse (EHR), as well as Local Control (LC) and Overall Survival (OS) rates, were evaluated. Results Forty-three patients with liver-only metastatic disease received SBRT. Most common primary tumors were breast cancer (n=18.42%) and colon cancer (n=10.23%). SBRT was performed using Cyberknife real-time tumor tracking (n=30,70%) or abdominal compression-assisted VMAT (n=13.30%) delivering 35-60 Gy in 3-5 fractions, corresponding to median EQD2 of 94 (50-150) Gy. Twelve (28%) patients were chemotherapy-naïve, while the remaining patients received 1 (20,46%), 2 (5,12%) or ≥ 3 (6,14%) chemotherapy lines. Median follow-up was 12 months. Patterns of failure are reported in Table 1 . +LR +IHR +EHR +IHR+EHR LR 0 12 0 9 IHR 12 2 11 / EHR 0 11 5 / IHR+EHR 9 / / / Table 1. One-year OS was 87%. At multivariate analysis LC was significantly correlated with EQD2 ≥ 94Gy (p=0.009) and ≥ 3 chemotherapy lines (p=0.04). IHR and EHR were significantly associated with local failure (p=0.0013) and intrahepatic progression (p=0.03), respectively. A significant correlation between OS and local relapse was shown (p=0.026). Kaplan Meier curves for these analyses are shown in Figure 1 .