ESTRO 2023 - Abstract Book

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ESTRO 2023

using Kaplan-Meyer curves and log rank testing. The cumulative incidence of local recurrence (LR) was estimated through the Kaplan-Meier method according to the Fine-Gray model. Toxicity was evaluated through CTCAE v 5.0 scale. Results Between 2014 and 2022, 27 patients were treated with SRT to 53 lesions for OMD or OPD during ICIs. OPD was found in 23 (85%) patients. 19 (70%) patients were male and 15 (56%) patients were older than 65 years. Initial diagnosis was melanoma, lung cancer, renal cancer and head and neck cancer in 10 (37%), 12 (44%), 4 (15%) and 1 (4%) patients respectively. Median SRT total dose was 27 Gy (range 24-30 Gy) delivered in 3 fractions (range 3-5) and irradiated metastatic lesions were in brain, lymph nodes, lung and others in 32 (60%), 9 (17%), 7(13%) and 5(9%), respectively. After SRT, patients were followed for a median follow up of 11.3 months. One-year PFS, TS-FS and OS were 39.5%, 45% and 73%, respectively (Figure 1).

Median PFS was 8.2 months and median OS was 18.3 months. Median TS-FS was 10.2 months, with an average Time to Treatment Switch (TTS) of 11 months for all patients who changed systemic therapy and an average TTS of 31.5 months for patients who underwent SRT two or more times for oligoprogressive disease. Concomitant chemotherapy, higher Charlson Comorbidity Index, brain as first site of SRT and low lymphocyte count were predictive factors of LR. Only four patients experienced treatment related toxicity (grade 1 to 3). Conclusion The combination stereotactic radiotherapy and immunotherapy is safe and allows to postpone the initiation of a new line of systemic therapy of about 11 months with a very favorable toxicity profile. Results in terms of survival are encouraging. Further research is needed to evaluate the optimal integration between immunotherapy and local therapies and SRT in particular as well as to identify predictive biomarkers. We aim at understanding the role of systemic inflammation biomarkers in this scenario. 1 Instituto Português de Oncologia do Porto, Radiotherapy, Porto, Portugal; 2 Centro Hospitalar Universitário São João, Radiotherapy, Porto, Portugal; 3 Instituto Português de Oncologia do Porto, Cancer Epidemiology Group-Research Center, Porto, Portugal Purpose or Objective Stereotactic body radiation therapy (SBRT) has an emerging role in the treatment of inoperable lung metastasis. This study aims to evaluate the efficacy of SBRT and identify prognostic factors influencing survival and local control. Materials and Methods Unicentric retrospective study, of 162 patients (250 lesions), with lung metastasis, treated with SBRT, between 2013 and 2020. Patients lost to follow-up were excluded. Primary and metastatic tumor characteristics, treatment and follow-up data were evaluated. Results The median age was 67 years and 64% were male. The primary tumor was mainly colorectal (65%), followed by breast (6.2%) and other origins (28%). Eighty seven per cent of patients presented metachronous metastasis. Sixty-four per cent were treated for a single metastasis, 32% for 2-3 and 4.3% for ≥ 3. The prescribed total dose was 30-34Gy in single fraction (49%) and 40-50Gy in 4 to 5 fractions. Sixty-five per cent of lesions were treated with a BED10 >100. Median total volume of metastasis was 2.2cc [0.088-104] and median diameter was 14mm [1.00-61.0]. The median follow-up was 32.5 months. Two and 5-years overall survival (OS) rates were 84.2% and 46.6%. For progression free survival (PFS), 2- and 5-years rates were 36.4% and 20.3% and for local control (LC) 80.9% and 75.1%, respectively. OS (p=0.97) and PFS (p=0.16) were not statistical different between colorectal cancer and other primary tumors. Colorectal cancer showed tendency for worst local control compared with other tumors (p=0.055). The first location of disease progression was: 54% regionally, 9.3% locoregionally and 6.2% regionally and at distance; 15% at the distance; 11% progression in the field. No patient experienced grade toxicity ≥ 3. At the univariate analysis, age ( ≥ 70 years) was a prognostic factor for regional-PFS (lung metastasis outside the SBRT treatment field; HR 0.42) and PFS (HR 0.55). The administration of systemic treatment previous to SBRT ( ≥ 3 lines) also presented statistical significance for regional-PFS (HR 2.46) and PFS (HR 2.23). The dimensions of metastasis, namely diameter ( ≥ 25mm) and volume ( ≥ 10cc) were predictive factors for worst OS (HR 2.77 and HR 3.50, respectively) and distance-PFS (HR 2.09 and HR 2.59, respectively). The presence of extrapulmonary disease (EPD) was a significative PO-1609 Lung metastasis treatment with Stereotactic Body Radiation Therapy: a single institution experience S. Costa 1 , F. Sousa 2 , P. Leite-Silva 3 , D. Gomes 1 , O. Sousa 1