ESTRO 2024 - Abstract Book

S1589

Clinical - Lung

ESTRO 2024

Umair Mahmood 1,2 , Eleni Josephides 1 , Nicholas Coupe 2 , Daniel Smith 1 , Shahreen Ahmad 1 , Omar Al-Sahili 1 , Sze M. Mak 3 , Meenali Chitnis 2 , Alexandros Georgiou 1 , Daniel Ajzensztejn 2 , James Spicer 4 , Eleni Karapanagiotou 1 , Geoff S. Higgins 2 , Niki Panakis 2 , Jonathan D. Schoenfeld 5 , Michael Skwarski 1 1 Guy’s and St. Thomas’ NHS Foundation Trust (GSTT), Department of Oncology, London, United Kingdom. 2 Oxford University Hospitals NHS Foundation Trust (OUH), Oxford Cancer and Haematology Centre, Oxford, United Kingdom. 3 Guy’s and St. Thomas’ NHS Foundation Trust (GSTT), Department of Radiology, London, United Kingdom. 4 King's College London, Guy's Hospital, London, United Kingdom. 5 Dana-Farber Cancer Institute, Department of Radiation Oncology, Boston, USA

Purpose/Objective:

We conducted the largest multi-national review to date evaluating clinical outcomes following radiotherapy for non small cell lung carcinoma (NSCLC) patients with oligoprogression on immune checkpoint inhibitors (ICIs).

Material/Methods:

We identified NSCLC patients with oligoprogression (defined as < 5 progressive lesions) while on ICIs and were managed with any dose of radiation between January 2010 – April 2023 at Guy’s and St. Thomas’ NHS Foundation Trust, Oxford University Hospitals NHS Foundation Trust and the Dana-Farber/Harvard Cancer Center. Patients were eligible if they received radiotherapy to all oligoprogressive disease (OPD) sites with other disease sites remaining stable or responsive to ICIs. Patients whose systemic therapy was changed after radiation, but before progression were excluded. Oligoprogressive lesions were identified radiologically using the RECIST v1.1 criteria, which was also used to determine post-radiotherapy response and subsequent disease progression. The evaluated outcomes comprised of local control (LC) of irradiated OPD lesions, progression-free survival (PFS) assessed as first progression from the date of first radiation fraction either at irradiated OPD lesion or other non-irradiated sites, and overall survival (OS). The three survival outcomes were calculated using Kaplan - Meier actuarial survival methods and Cox proportional-hazards models using R in RStudio software. We screened 1178 NSCLC patients who had received ICIs and radiotherapy and identified 103 eligible patients. To our knowledge, this represents the largest dataset compiled to date in the current clinical setting. The median number of oligoprogressive lesions was 1 and the most common anatomic site of OPD was lung (N = 33). The most frequently prescribed ICI agent before OPD diagnosis was pembrolizumab monotherapy (N = 53). The median duration of last ICI therapy before OPD diagnosis was 5.55 months. The median LC of irradiated oligoprogressive lesions was not reached. Median PFS and OS were 6.90 (95% Confidence Interval, 5.75 - 12.91) and 23.46 (95% Confidence Interval, 17.54 - 37.16) months, respectively. Patient specific factors comprising of age, gender, smoking status, programmed death-ligand 1 tumour proportion score, KRAS mutational status, number of oligoprogressive lesions and cumulative tumour volume were not associated with any of the three survival outcomes (Table 1). Treatment-specific factors including radiation modality and response of oligoprogressive lesions to prior ICIs before radiation also lacked an association with these survival outcomes (Table 2). However, LC was associated with intermediate radiation doses (Equivalent Dose in 2 Gy Fractions (EQD2); > 40 Gy and < 80 Gy, α/β = 10) (P = 0.01) and local response to radiation (P = 0.007). Improved PFS Results: