ESTRO 2022 - Abstract Book

S1065

Abstract book

ESTRO 2022

Conclusion SBRT in lung cancer patients for oligoprogression resulted in a long median overall survival of 26 months. Local control at 1 year was 82%. The median DFS was 6 months as other metastases grow slowely. SBRT could be a valid alternative to postpone the change of chemotherapy and/or immunotherapy. More research is needed to address the gain of the SBRT in patients with oligoprogressive disease.

PO-1262 Early response to chemotherapy as predictor of locoregional and distant failure in NSCLC

M. Tvilum 1 , M.M. Knap 1 , C.M. Lutz 2 , L. Hoffmann 2 , A.A. Khalil 1 , A. Haraldsen 3 , M. Alber 4 , C. Grau 1,5 , H.H. Schmidt 1 , M. Kandi 1 , L.S. Mortensen 1 , M.I. Holt 1 , A. Appelt 6 , D.S. Moeller 1 1 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; 2 Aarhus University Hospital, Department of Medical Physics, Aarhus, Denmark; 3 Aarhus University Hospital, Department of Nuclear Medicine and PET, Aarhus, Denmark; 4 Heidelberg University Clinic, Department of Radiation Oncology, Heidelberg, Germany; 5 Aarhus University Hospital, Danish Center for Particle Therapy, Aarhus, Denmark; 6 University of Leeds, Institute of Medical Research at St James’s, Leeds, United Kingdom Purpose or Objective Combined chemo-radiotherapy (cRT) is standard of care for patients with locally advanced non-small cell lung cancer (LA- NSCLC). This study evaluates the early radiologic and metabolic tumour response after chemotherapy and its prognostic value in predicting pattern of failure for LA-NSCLC-patients. Materials and Methods Patients with LA-NSCLC treated with curative intended cRT (2012-2019) at a single institution were retrospectively reviewed (n=188). All patients had diagnostic PET/CT-(dPC) and planning PET/CT (pPC)-scans, between which they received platinum-based chemotherapy. Volume, sphericity and SUV peak for the gross tumour volume (GTV-T) were investigated on dPC and pPC. First failure was characterized as either loco-regional (LR), distant metastasis (M), simultaneous (LR+M) or death with no evidence of disease. Two multivariate competing risk analyses (Fine-Gray model) were performed, including patient characteristics only (Model 1) and patient characteristics, baseline and changes of image features (Model 2). The variables included are given in Fig. 1. The models are described with sub-distribution hazard ratios (SHR) with 95%- Confidence intervals for each failure mode. Cumulative incidences were plotted for discrete subgroups with the strongest effects in multivariable modelling and a Fine and Gray test was used to test for difference in each of the outcomes. Results Median follow-up for patients alive was 33 months. Baseline image features on dPC as well as changes between dPC and pPC in response to chemotherapy varied greatly. Median decrease in GTV-T volume and SUV peak were 19.1% and 32.7%, respectively (fig. 1). In Model 1, histology was the only significant prognostic factor. Squamous cell carcinomas (SCC) presented a significantly lower risk of M failure (SHR=0.246 [0.0887-0.684], p<0.01), and higher risk of LR failure (SHR=2.15 [1.09-4.21], p=0.026) compared to adenocarcinomas (AC). In Model 2, SUV peak at diagnosis was the only significant predictor of LR failure (SHR=1.07 [1.02-1.13], p<0.01), while histology was still the significant predictor of M failure (SHR=0.259 [0.0970-0.694], p<0.01, SCC). Analysis on four subgroups (histology, SUV peak above and below median) by Fine and Gray tests showed significant difference for LR (p<0.01), M (p<0.01) and LR+M failure (p=0.048) between the four groups. Cumulative incidence plots for the four subgroups (fig. 2) illustrate that the incidence of M failure varies with histology, but not with SUV peak . For LR failure, ACs with high SUV peak are notably more prone to failure than ACs with low SUV peak . For SCC, the incidence of LR failure is independent of SUV peak .