ESTRO 36 Abstract Book

S665 ESTRO 36 _______________________________________________________________________________________________

Widder 1 1 University Medical Center Groningen, Radiation Oncology, Groningen, The Netherlands Purpose or Objective Survival results for limited-stage-SCLC are more favourable for accelerated BID compared with OD chemoradiotherapy (CRT) to nominally equal doses (Turrisi et al. NEJM 1999), but were not further improved by escalating once-daily doses from 45 Gy to 66 Gy (CONVERT-trial). However, concerns regarding acute toxicity with BID CRT do exist. We report prospectively assessed patient-reported outcome measures (PROMs) on dysphagia and dyspnea from an institutional cohort where patients receive BID CRT as preferred treatment, and OD in case of adverse patient- or tumour-related baseline factors suggesting they would not tolerate the accelerated schedule. Material and Methods All consecutive patients with LS-SCLC treated with VMAT/IMRT or 3D-CRT between 2013 and 2016 within our prospective data registration program (clinicaltrials.gov) were included. The BID schedule was given in 3 weeks to 45 Gy (30*1.5 Gy), OD CRT was given in 5 weeks to 45–50 Gy (25*1.8–2.0 Gy), concurrent or sequential cisplatin- etoposide was scheduled with both regimens. The primary endpoint was PROM-dysphagia within (acute) and after 3 months of inclusion (late). Secondary endpoints were PROM-dyspnea, physician-rated dysphagia, radiation pneumonitis, and survival. Toxicities were related with esophageal and pulmonary DVH-parameters, respectively. Results Out of 74 patients, 38 received BID and 36 received OD CRT with no difference in number of cisplatin-etoposide cycles between groups. In line with the institutional policy, the BID cohort was younger (62 versus 68 years, p=0.017), had smaller tumour volumes at planning CT (79 cc versus 127 cc, p=0.056), and tended to be in a better general WHO performance status (PS) (45% versus 25% at PS 0, p=0.075). At median follow-up of 9.4 months for surviving patients, unadjusted as well as adjusted survival (adjusted for age, WHO PS, stage and GTV) was not significantly better for BID (HR=0.60, 95%CI 0.3–1.4 and HR=0.70, 95%CI 0.3–1.8, respectively). PROMs regarding dysphagia and dyspnea as well as physician-rated toxicities and radiation pneumonitis were not different between groups (figure). Mean esophageal V35 and mean pulmonary V20 were different between BID and OD cohorts (30 Gy versus 41 Gy; p=0.027, and 20 Gy versus 23 Gy; p=0.061, respectively), in line with GTV differences between groups.

differ between BID and OD CRT. Treatment allocation could be further improved by dose-volume-fractionation modelling for esophagitis. EP-1233 Early results of SBRT as a salvage treatment after thoracic radiotherapy. A. Navarro-Martin 1 , I. Guix 1 , J. Mases 1 , M. Mutto 2 , E. Nadal 3 , F. Guedea 1 1 Institut Català d'Oncologia, Radiation Oncology, L'Hospitalet de Llobregat, Spain 2 European Oncology Institue, Radiation Oncology, Milano, Italy 3 Institut Català d'Oncologia, Medical Oncology, L'Hospitalet de Llobregat, Spain Purpose or Objective Isolated intrathoracic relapse is common across distinct tumors and especially in lung cancer. Patients who received previous radiotherapy treatment (PRT) are not suitable for salvage surgery and chemotherapy provides poor local control. This study aimed to assess the toxicity and outcome of SBRT re-irradiation (reRT) in patients with solid tumors who developed an intrathoracic relapse. Material and Methods 35p treated with PRT who received salvage SBRT were identified in our database and their medical records were retrospectively reviewed. All patients underwent complete pulmonary function tests (cPFTs) (including DLCO, FEV1 and FVC) and PET-CT scan was performed before and after receiving lung reRT. Treatment planning was based on image fusion with the previous treatment plan and calculating the cumulative total nominal dose. Survival estimations were performed using Kaplan-Meier and differences between PFTs prior and post-reRT were analyzed using Student T-Test. Early toxicity was defined when it occurred up to 6 months. Results Median age: 68 (r53-81); 29p (83%) were male The previous treatments SBRT in 17p (49%), 3D-RT 4p (11%) and CT+RT 14p (40%) Mean RT dose 60,4Gy (r34-74). Primary tumors: lung 24 (69%), colorectal 9 (25%), oesophagus 2 (6%). For lung cancer p, the stage distribution was: IA 8 (23%), IB 2 (6%), IIA 2 (5.7%), IIB 1 (3%), IIIA 5 (4%), IIIb 4 (11%), IV 2 (6%). For other primaries, 8p (23%) were non metastatic at diagnosis and developed oligoprogressive disease in thorax which was treated with SBRT and 3 (8.5%) were oligometastatic. The location of reRT site: same lobe 17 (48%), ipsilateral different lobe 7 (20%), contralateral lobes 11 (32%). Median delivered dose of salvage SBRT was 50Gy (50-60) in 10 fractions (r3-10). Median accumulated dose in the lung was 81Gy (r60.10Gy-176Gy). With a median follow-up of 10m local control rate was 74% (IC95%; 0.59-0.9) and 1-year OS was 84% (IC 95%;0.67-1). The metabolic complete response rate was 23%. No differences in the baseline and post re-irradiation PFTs were observed: FEV1, FVC and DLCO difference and CI95% were 2.41 (-1.79-6.62); 65 (-125-257) and 12.5 (-95 - 121). Asthenia GII in 12p (31%) was the most frequent acute toxicity, no long-term toxicities were detected. Conclusion Salvage SBRT for treating isolated intrathoracic relapses achieved an outstanding local control and overall survival in selected p . This treatment did not impair post- reirradiation PFT and long-term toxicities were not observed. EP-1234 Prophylactic Cranial Irradiation (PCI) in Small- Cell Lung Cancer: a single-institution experience. M. Konkol 1 , M. Matecka-Nowak 1 , M. Trojanowski 2 , A. Kubiak 2 , P. Milecki 1 1 Greater Poland Cancer Centre, I Radiotherapy Dept., Poznan, Poland

Conclusion Treatment selection based on tumour volume and patient condition effectively limited PROMs and physician-rated acute and late dysphagia in BID CRT. This can be explained by the significantly lower esophageal V35 due to smaller GTVs in patients receiving BID treatment. Also, acute and late PROM-dyspnea and radiation pneumonitis did not