ESTRO 2021 Abstract Book

S759

ESTRO 2021

Results A total of 149 patients with 414 liver metastases were treated at our institution. Colorectal adenocarcinoma was the most frequent histology 64.4%, followed by pancreas and breast cancer (8.1 and 5.4 % respectively). Median PTV volume was 40.47 cc; 44.3% were treated of single metastases whereas 18.1% of two and 37.6% of three or more (3-14). With an average follow-up of 24 months (1-138), actuarial local control (LC) was 76.1% and 61.2% at 2 and 3 years respectively, no local relapse was founded after three years and median LC was not yet reached. In multivariate analyses, colorectal histology, prescription dose (BED 10 ≤100Gy), and presence of new liver metastases were associated with lower LC. Median overall survival (OS) was 32 months (95%CI 27.6-36.3). In multivariate analyses, the presence of other metastatic sites at the time of SBRT and a trend towards the appearance of new metastases after SBRT (p=0.053) was correlated with OS. Median Disease-free survival was 10 months (95% CI=7.7-12.2) (Figure 2). Acute Grade IV thrombopenia was observed in one patient, with no other major (G III/IV) acute toxicity recorded. Chronic toxicity was seen in 2.7 % of the patients as grade I and III rib pain, and grade II muscular pain.

Conclusion SBRT for liver metastases is a safe and secure treatment for either single or multiple liver metastases. High LC was achieved in selected oligometastatic patients with a long survival expectancy (OS=32 months). BED 10 ≤100Gy and colorectal histology were related to LC and the presence of metastases outside the liver at SBRT to OS. Further randomized studies are necessary to confirm those findings and create guidelines to select those patients who more benefits from this promising treatment technique.

PD-0918 Stereobody radiotherapy vs chemoradiation in elderly with locally advanced pancreatic cancer. F. Bertini 1,2 , A. Arcelli 1,3 , M. Buwenge 1,3 , G. Macchia 4 , A. Guido 1 , G. Tolento 1 , F. Deodato 4,5 , S. Cilla 6 , V.