ESTRO 2022 - Abstract Book

S1078

Abstract book

ESTRO 2022

Purpose or Objective To assess progression-free survival (PFS) and recurrence patterns after concurrent chemoradiotherapy (CCRT) followed by durvalumab in patients with non-small cell lung cancer (NSCLC). Materials and Methods We conducted a multicenter retrospective study at 15 institutions in Japan. Patients receiving CCRT (prescribed dose ≥ 54 Gy) between July 2018 and July 2019 and consolidation durvalumab for stage III or postoperative recurrent NSCLC were enrolled. Results One hundred thirty-eight patients were eligible for the study. With a median follow-up period of 28.9 months [interquartile range, 25.1–32.2 months], the 24-month PFS rate was 40.4% (95% confidence interval, 33.0–49.6%). The multivariate analysis showed that the period from the last day of radiotherapy to durvalumab start ≥ 14 days and gross tumor volume (GTV) ≥ 56 cm 3 were significantly associated with shorter PFS (P = 0.04 and 0.04, respectively). Among the eligible patients, 79 patients (57.2%) experienced any recurrences. Loco-regional recurrence as the initial recurrence occurred in 41 (29.7%) including 34 in-field recurrences (where ≥ 90% of the prescribed dose was irradiated). Squamous cell carcinoma and programmed cell death-ligand 1 (PD-L1) expression status < 50% were significantly associated with the in-field recurrence (P = 0.003 and 0.012, respectively). Distant metastasis occurred in 53 patients (38.4%). The most common sites were brain (16 patients), lung (13 patients), and adrenal gland (10 patients). Conclusion The real-world outcomes of Japanese patients with NSCLC treated with CCRT followed by durvalumab were consistent with the results reported in the PACIFIC trial. In-field recurrence is still a major problem after CCRT followed by durvalumab, and histological subtype and PD-L1 expression could be clues to an optimal treatment strategy for improving the outcomes. 1 Maastro, Radiation Oncology, Maastricht, The Netherlands; 2 MUMC+, Pulmonology, Maastricht, The Netherlands; 3 MUMC+, Thoracic surgery, Maastricht, The Netherlands Purpose or Objective Radiotherapy (RT) for thymic epithelial tumors (TET), including thymoma and thymic carcinoma, is indicated postoperatively for advanced/aggressive disease or incomplete resection, or as primary treatment in inoperable patients (ESMO guideline). Proton therapy has the potential to better spare normal tissues compared to photons, and hence reduce toxicity. The aim of this study is to compare photon and proton plans regarding doses, normal tissue complication probability (NTCP), and report acute toxicity in TET-patients treated with RT at our center. Materials and Methods All patients with TET who were referred for RT from 08.2019 until 08.2021 were included. Intensity-modulated proton therapy (IMPT) and volumetric arc photon therapy (VMAT) plans were compared regarding mean doses to the lungs (MLD), heart (MHD) and esophagus (MED) (using paired t-test), and normal tissue complication probability (NTCP) with endpoints radiation pneumonitis 1 , cardiac toxicity 2 and acute dysphagia 3 . In The Netherlands, patients are selected for IMPT if the NTCP is significantly lower, by consensus i.e. ≥ 10% for radiation pneumonitis or acute dysphagia, or ≥ 2% lower for cardiac toxicity 4 . Maximal acute toxicity for dermatitis and dysphagia according to CTCAE is reported. VMAT plans consisted typically of 2-3 partial 6MV arcs in the anterior region, and the dose was prescribed to the PTV. IMPT plans were typically administered with 3 or 4 anterior and anterior oblique beams going from 300° to 50°; robust optimization was used. PO-1280 Clinical benefits of proton therapy in thymic epithelial tumors using a model-based approach S. Peeters 1 , E. Kneepkens 1 , F. Marcuse 2 , M. Hochstenbag 2 , J. Maessen 3 , D. De Ruysscher 1

Results Thirteen TET patients had a VMAT-IMPT planning comparison. Patient characteristics are shown in Table 1.