ESTRO 2023 - Abstract Book

S812

Monday 15 May 2023

ESTRO 2023

Cooperative Oncology Group (ECOG) performance status (PS) of 0–2. Of the 56 total lesions, primary cancer was lung in 57%, colon-rectal in 16%, not-typable in 11%, breast in 9%, endometrial and oropharyngeal in 3.5% respectively. Thirty-four lesions were treated in the same lobe, 12 in the ipsilateral lobe, 10 in the contralateral lung. Fifty-four lesions were peripherally located and 2 had a central location. Medium volume of clinical target volume (CTV) was 32.75 cc (range: 0.89-260.77). Medium BED10 of re-irradiation was 97.8 Gy (range: 37.5-151.2) and medium EQD210 was 82.18 Gy (range: 31.25-126). Thirteen lesions were re-irradiated with a single fraction, 43 with multiple fractions (range: 3-10). The most represented schedules in all subsequent courses of SBRT were 30 Gy in 1 fraction, 45 Gy in 3 fractions and 54 Gy in 3 fractions. Results After a median follow-up of 24.8 months (range: 3.2-141.7), Local Control (LC) was 53.2% at 1-year, 50.6% at 2-years and 35.5% at 3-years. Progression Free Survival (PFS) was 37.8% at 1- year, 28.1% at 2-years and 10.5% at 3-years. Disease Specific Survival (DSS) was 76.6 % at 1-year, 47.4% at 2-years and 36.9% at 3-years. Overall Survival (OS) was 78.3% at 1 year, 49.5% at 2-years and 40.1% at 3-years. On univariate analysis, CTV volume ≥ 33cc was statistically significantly related to LC (p=0.0157) and PFS (p=0.0106). Total number of treatments on lungs had a statistically significant correlation to PFS (p=0.0188), DSS (p=0.0007) and OS (p=0.0017). Number of re-irradiations was significantly related to PFS (p=0.0300) and DSS (p=0.0011).

Conclusion Our experience showed favorable long-term outcomes in pts retreated on lung with SBRT. Data on role of SBRT in recurrent setting are limited and further studies are necessary to confirm feasibility and safety of this approach. PD-0964 SBRT of lung and liver oligometastases from breast cancer:a prospective non-randomized phase 2 trial B. Marini 1,2 , L. Di Cristina 1,2 , V. Vernier 1,2 , R. Spoto 1 , L. Dominici 1 , F. Lobefalo 3 , L. Paganini 1 , C. Franzese 1,4 , D. Franceschini 1 , M. Scorsetti 1,4 1 IRCCS Humanitas Research Hospital, Radiotherapy and Radiosurgery, Rozzano, Milan, Italy; 2 Humanitas University, Department of Biomedical Sciences, Pieve Emanuele, Milan, Italy; 3 IRCCS Humanitas Research Hospital, Radiotherapy and Radiosurgery, Rozzano, Milan, Italy; 4 Humanitas Univesity, Department of Biomedical Sciences, Pieve Emanuele, Milan, Italy Purpose or Objective We report mature toxicity and preliminary efficacy data from a phase II non randomized trial assessing the use of SBRT for lung and liver oligometastases from breast cancer. The co-primary endpoints were local control (LC) and both acute and late toxicity rates. Secondary endpoints were represented by distant progression free survival (DPFS), overall survival (OS), polyprogression free survival (PoFS), and time to start or change systemic therapy. Materials and Methods Oligometastatic patients from breast cancer were treated with SBRT for up to 5 lung and/or liver lesions. Inclusion criteria were: age >18 years, ECOG 0-2, absence of life-threatening conditions, diagnosis of breast cancer, less than 5 lung/liver lesions (with a maximum diameter <5 cm), metastatic disease confined to the lungs and liver or extrapulmonary or extrahepatic disease stable or responding to systemic therapy, chemotherapy completed at least 3 weeks before treatment or started at least 2 weeks after RT, written informed consent. Different dose-fractionation schedules were used. 4D-CT scan and FDG-CT PET were acquired for simulation and fused for target definition. Results From 2015 to 2021, 64 patients for a total of 90 lesions were irradiated. Main patients and treatment characteristics are shown in table 1. Treatment was well tolerated, with no G3-4 toxicities. Acute and late toxicities are reported in table 2. Median follow-up was 19.4 months (range 2.6 – 73.1). LC rates were 96.2% at 1 and 3 years. Complete response, partial response and stable disease were detected in 39 (61%), 19 (30%), 6 (9%) patients, respectively. Median OS was 29.7 months. OS rates at 1 and 3 years were 86.5% and 45.8%. Median DPFS was 7.96 months, with a DPFS rate at 1 and 3 years of 35.5% and 18.77%. Median PoFS was 14.5 months, with a PoFS rate at 1 and 3 years of 64% and 23.5%. The median time to next systemic therapy was 7.9 months, with a 1-year rate of 30% and a 3-years rate of 2.5%. Kaplan-Meier curves for local control, distant progression free survival and overall survival are represented in Figure 3 through 5. In univariate analysis, the presence of extra-target lesions demonstrated a significant impact on OS, DPFS, and PoFS. Hormone-sensitive primary tumors were associated with a longer time to systemic therapy.