ESTRO 2024 - Abstract Book

S1651

Clinical - Lung

ESTRO 2024

Eleni Gkika 1 , Elke Firat 1 , Sonja Adebahr 1 , Ilinca Popp 1 , Erika Graf 2 , Alexandra Eichhorst 1 , Gianluca Radicioni 1 , Simon Spohn 1 , Nils Nicolay 3 , Simon S. Lo 4 , Ursula Nestle 1 , Gabriele Niederman 1 , Dan Duda 5 , Anca-Ligia Grosu 1 1 University Medical Center Freiburg, Radiation Oncology, Freiburg, Germany. 2 University Medical Center Freiburg, IMBI, Freiburg, Germany. 3 University Medical Center Freiburg, Radiation Oncology, freiburg, Germany. 4 University of Washington School of Medicine, Department of Radiation Oncology, Seattle, USA. 5 E. L. Steele Laboratories for Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School,, Boston, USA

Purpose/Objective:

The study aimed to evaluate the impact of ablative SBRT on systemic immunity in patients with early-stage NSCLC or oligoprogressive or oligometastatic lung disease, using different dose and fractionation regimes, with or without systemic treatment.

Material/Methods:

Patients with lung SBRT either in the primary or the metastatic setting with or without concurrent systemic treatment were included in the prospective LAPIS trial (Lung and Liver cancer, Ablative high Precision radiotherapy and the Immune System-DRKS 00011266).in order to evaluate the immune effects of SBRT immunoprofiling of peripheral blood was performed at the first SBRT fraction (baseline), during and at the end of SBRT as well as at first (FU1) and second (FU2) follow-up.

Results:

The LAPIS trial accrued 156 patients between 2016-2021, of whom 130 were evaluable by flow cytometry. With a median follow-up of 30 months, the median overall survival (OS) was 38 months from SBRT, and the median progression-free survival (PFS) was 14 months, while the 3- and 5-year PFS were 33% and 23%, respectively. Patients treated with less than 10 Gy showed a significant increase in the proportion of CD8+ and CD4+ proliferating T-cells compared to pre-treatment values at the end of treatment and follow-up. At the same time, this effect was not seen in patients treated with 10 Gy or more, and it was most prominent at a fractionation of 8 x 7.5 Gy. These increases were durable and were observed at follow-up especially in the subgroup of patients with metastatic disease without concurrent systemic treatment.

Conclusion:

This prospective study indicates that SBRT can significantly influence the peripheral immune response. Furthermore, ower doses per fraction such as 8 x 7.5 Gy are most potent in inducing increases in proliferating T cells' frequency after SBRT. The optimal sequencing for combining systemic treatment may be at the end of SBRT.

Keywords: SBRT, Immune modulation, lung. Immunotherapy