ESTRO 2023 - Abstract Book

S1046

Digital Posters

ESTRO 2023

Conclusion There is no randomised evidence to guide practice. Whilst there was some variation in management detected, the European guidelines were largely adopted. A larger national cohort is being investigated. Consideration should be made to make management decisions within national MDTs involving clinicians with an interest in the management of thymoma.

PO-1305 Pattern of failure of LD-SCLC treated with chemoradiotherapy: dependence on disease stage.

H.H. Schmidt 1 , D.S. Moeller 1 , L. Hoffmann 1 , C.M. Lutz 1 , M. Kandi 2 , L.S. Mortensen 1 , M. Tvilum 1 , A. Khalil 1 , M.M. Knap 1

1 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; 2 Goedstrup Hospital, Department of Oncology, Herning, Denmark Purpose or Objective The standard treatment for limited-disease small-cell lung cancer (LD-SCLC) is platinum-based chemotherapy concurrent with hyperfractionated radiotherapy (RT) followed by prophylactic cranial irradiation. Despite treatment with curative intent, locoregional as well as metastatic relapse are frequent, and associated with a poor survival. The aim of this study was to investigate pattern of failure and survival for different disease stages in LD-SCLC patients with regard to potential benefits of individualized treatment regimes. Materials and Methods This retrospective study included 168 consecutive patients (86 men and 82 women) with LD-SCLC treated from 2012 to 2019. Median [range] age was 67 years [40-83] at diagnosis and performance status (PS) was 0-1 (85%), 2 (14%) and 3 (1%). Disease stage was I/II (15%), IIIa (30%), IIIb/IIIc (55%). Chemotherapy consisted of 1-4 cycles of cis/carboplatin on day 1 and intravenous etoposide on day 1-3 every 3 weeks. The tumor and pathological lymph nodes received 45 Gy/30F/10w. Delineation and treatment planning were based on a planning PET/4D-CT scan. Patients were set up based on daily conebeam CT. The patients were split into two groups, stage Ib+II+IIIa (group A) and stage IIIb+IIIc (group B). Kaplan-Meier curves were plotted for OS and compared using log-rank test. Overall survival (OS) was defined as the time from RT start until death. First failure was characterized as either loco-regional (LR), distant metastasis (M), simultaneous (LR+M) or death with no evidence of disease (DNED). The first site of failure in groups A and B was shown as cumulative incidences in stacked plots. Results Of all patients, 99% received chemotherapy, 88% concurrent with RT. With a Median follow-up of 54 months, the median overall survival (mOS) was 22.3 months for the entire group with a 2-year survival rate of 47.6 %. mOS was significantly longer in Group A (27.5 months, 2-year survival rate 57 %) than in Group B (20.3 months, 2-year survival rate 40%), p=0.018, see figure 1. At two years, the risk of isolated loco-regional failure is only slightly higher in group A (13 %) compared to group B (9%), see figure 2, while both isolated M and simultaneous LR+M are lower in group A (16% and 13%) compared to group B (27% and 27%). DNED are similar in the two groups (13% and 11%). After the first six months, 24% of patients in group B presented with metastatic disease compared to 8% in group A. Conclusion OS and pattern of failure differ between the two groups. Patients with more advanced disease (stage IIIb or IIIc) have a higher risk for metastatic disease and for simultaneous failures than patients with less advanced disease (stage I-IIIa), while isolated locoregional recurrences were more frequent for lower stage disease. These differences in pattern of failure should be considered in future trials. 1 Aarhus University Hospital, Danish Center for Particle Therapy, Aarhus, Denmark; 2 Aarhus University Hospital, Dept. of Oncology, Aarhus , Denmark; 3 Aarhus University Hospital, Dept. of Oncology, Aarhus, Denmark; 4 Aarhus University Hospital, Dept. of Medical Physics, Aarhus, Denmark; 5 University of Leeds, Institute of Medical Research at St. James's, Leeds, United Kingdom Purpose or Objective Patients with locally advanced (LA) non-small cell lung cancer (NSCLC) are treated with curatively intended combined chemo-radiotherapy (cCRT). However, overall- and progression-free survival remain poor. Selecting patients for treatment intensification could be the key to improve outcome for this group of patients. To date, imaging features are only rarely used for treatment intensification, as reliable correlations have yet to be established. This study investigates whether radiologic and metabolic response to induction chemotherapy can predict freedom from progression in patients with LA NSCLC treated with cCRT. Materials and Methods Patients with LA NSCLC treated with cCRT at a single institution were included for analysis (n=199). Baseline diagnostic (dPCT) PET-CT and planning (pPCT) PET/CT-scans were collected. Patients received induction platinum-based chemotherapy between the two scans. Inclusion criteria for this study were treatment with ≥ 60 Gy RT dose, and no surgical intervention. Gross tumour volume (GTV-T) was delineated at pPCT, deformably transferred to dPCT, and corrected if PO-1306 Response to induction chemotherapy on PET/CT predicts post-RT progression in patients with NSCLC M. Tvilum 1 , M.M. Knap 2 , A.A. Khalil 3 , L. Hoffmann 4 , C.M. Lutz 4 , A. Appelt 5 , H.H. Schmidt 3 , D.S. Møller 4