S836
Clinical - Lung
ESTRO 2026
Digital Poster 4200 Radiologic and metabolic tumor responses in patients with limited disease small cell lung cancer – prognostic potential Sara Linde 1,2 , Christina M Lutz 1 , Simon N Thomsen 1,2 , Hjørdis H Schmidt 1 , Lone Hoffmann 1,2 , Marianne M Knap 1 , Ditte S Møller 1,2 1 Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. 2 Department of Clinical Medicine, Aarhus University, Aarhus, Denmark Purpose/Objective: Despite treatment with curative intent, the prognosis of patients with limited disease small cell lung cancer (LD-SCLC) is poor due to high local and distant failure rates. Identification of patients with a higher failure risk is challenging but could guide a more patient individualized treatment. Small studies indicate a correlation between radiologic and metabolic initial response to treatment and high risk of failure. Therefore, we aimed to explore the prognostic potential of initial radiologic and metabolic tumor responses in our cohort of patients treated with curative intent for LD-SCLC. Material/Methods: A total of 106 patients were treated with chemoradiotherapy with a curative intent over a five- year period (January 2016 to December 2020) at Aarhus University Hospital for LD-SCLC. 18F- deoxyglucose PET-CT scans from diagnosis (dPET-CT) and radiotherapy treatment planning (pPET-CT) were obtained. Primary tumors were delineated on both dPET-CT and pPET-CT. Pattern of first failure was noted as either no failure (NOf), loco-regional failure alone (LRf), both loco-regional and distant failure (LR+Df) or distant failure alone (Df). Radiologic (volume, surface area, and maximum diameter) and metabolic (SUVpeak, SUVmax, and SUVmean) parameters of the primary tumors were extracted from dPET-CT and pPET-CT. Initial treatment responses as a percentage change from dPET-CT to pPET-CT were compared by Kruskal Wallis Test for the failure groups. Results: Of the 106 patients, all scans and a primary tumor site were available for 93 patients. Median tumor volume difference from dPET-CT to pPET-CT was -13ml [- 358;12] corresponding to a median change of -46% [- 94;58]. Median SUVpeak difference was -5 [-32;4] corresponding to a median change of -50% [-93;121]. Median follow-up time was 61 months. Of the 93 patients, 29 (31%) had NOf, 9 (10%) had LRf, 26 (28%) had LR+Df, and 29 (31%) had Df. No statistically significant difference between groups was observed for initial treatment responses of tumor size and SUV uptake parameters, see table 1. However, visual
applied: (1) rigid fusion of the two planning CTs; (2) cumulative OAR and target dose evaluation using BED with α / β of 10 (tumour) and 2-3 for OARs Fig.1 (3) plan acceptance against predefined cumulative DVCs (Fig.2.). To account for registration uncertainty, OAR maxima were assessed on each OAR’s 5mm PRVs. Toxicities were recorded for the incidence of grade ≥ 1 toxicities in order to validate long-term clinical outcomes of the predetermined DVCs using this approach. Results:
Of the 726 screened irradiations, 110 patients met type 1 criteria. Median follow up time at 6.7 months (Range 0 -74 months) toxicity grade 1-3 = 9%, grade 4 =0% and grade 5 = 2.7%. For Grade 5 toxicities only pulmonary acute toxicities were observed. For all patients no serial organs toxicities were seen using the predefined DVCs from Fig.2. With regards to pulmonary toxicities the combined and most current treatment Lungs – GTV v20Gy mean was 19% and 8.8% respectively and therefore not able to discriminate in patients with high toxicity. Conclusion: This study formalises SLRON’s standardised SABR thoracic re-irradiation protocol on an international stage, demonstrating its safety and reproducibility. The limitations of the study include the fact this is retrospective data and to increase the follow-up to 24 months to further validate toxicity incidence. For these patients the results provide a validated foundation for further refining of DVCs, potentially expanding treatment eligibility for patients requiring thoracic re-irradiation. References: 1.Evaluation of Radical Thoracic Re-Irradiation: A Single Institution Retrospective Study. Geary, R.L. et al. International Journal of Radiation Oncology, Biology, Physics, Volume 114, Issue 3, e362 - e3632. The lessons of QUANTEC: recommendations for reporting and gathering data on dose-volume dependencies of treatment outcome.Jackson A et al. International Journal of Radiation Oncology, Biology, Physics,. 2010 Mar 1;76(3 Suppl):S155-60. Keywords: Toxicity, Reirradiation, Thoracic Lung
Made with FlippingBook - Share PDF online