ESTRO 38 Abstract book

S731 ESTRO 38

Esophagitis influences quality of life and might cause weight loss, treatment interruption and, in severe cases, hospitalization. Previous studies of risk factors mainly relate to curative treatment for non-small cell lung cancer (NSCLC), which often involves concomitant chemoradiation (CRT). Given the uncertainty around extrapolation of dose constraints, we analyzed risk factors in patients treated with hypofractionated palliative regimens, mainly for stage III and IV disease. Material and Methods A retrospective review of 106 patients treated with palliative 3-D conformal radiotherapy or CRT between 2009 and 2017 was performed. Inclusion criteria: prescribed total dose 30-54 Gy, dose per fraction 2.5-4 Gy (once daily, five fractions per week), esophageal dose >1 Gy. Uni- and multivariate analyses were performed to identify predictive factors for esophagitis grade ≥1 (CTCAE 5.0). Clinical information was abstracted from our electronic patient record system. All patients were followed during treatment by oncology nurses and physicians. Treatment plans were calculated with Varian Eclipse TPS. Results Forty percent of patients were treated with 15 fractions of 2.8 Gy (42 Gy) and 30% also received chemotherapy according to the CONRAD study regimen (induction and concomittant Carboplatin/Vinorelbine) published by the Norwegian Lung Cancer Group. Thirty-four percent were treated with 10 fractions of 3 Gy. Stage IV NSCLC was present in 47%. Esophagus Dmax was 39 Gy (population median) and Dmean 15 Gy. Overall 31% of patients developed esophagitis (26% grade 2-3, no grade 4-5). Several dosimetric parameters correlated with the risk of esophagitis (Dmax, Dmean, D5cc, V20, V30, V35, V40). Dmax outperformed other dosimetric variables in multivariate analysis. Furthermore, concomitant chemotherapy significantly increased the risk of esophagitis (for Dmax >39 Gy from 23 to 46%), while oral steroid medication reduced it (all p<0.05 in multivariate analysis). Age, gender and smoking were not significantly associated with esophagitis. When using general NSCLC dose constraints for mean esophagus dose the following rates of grade 2-3 esophagitis were observed: 29% for mean <34 Gy and 22% for mean ≤28 Gy. In contrast, mean <20 Gy resulted in 11% and mean <15 Gy in 5%. Median actuarial overall survival was 12 months in the CRT cohort and 7 months after RT alone (log-rank p=0.05). Conclusion In order to reduce the rates of grade ≥2 esophagitis after hypofractionated palliative treatment lower mean doses than those recommended in other NSCLC settings are preferable. Besides esophageal dose, CRT is the main risk factor for esophagitis. However, CRT also prolongs survival. Additional work is needed to confirm that steroids are able to modify the risk (or to rule out confounding effects of baseline variables not included in our database). EP-1335 Interaction of V20 and SUVmax as a predictor of lung toxicity D. Scepanovic 1 , A. Masarykova 1 , P. Povinec 2 1 National Cancer Institute, Radiation Oncology, Bratislava, Slovakia ; 2 PET Centrum BIONT- a. s., Nuclear Medicine, Bratislava, Slovakia Purpose or Objective The present study aimed to determine if bilateral lung V20 (volume of the whole lung receiving ≥ 20 Gy) in conection with the standardized uptake value (SUV) determined with 18F-FDG PET/CT can be used to predict radiation pneumonitis (RP) in lung cancer patients who received

were used to determine end diastolic volume (EDV) and end systolic volumes (ESV), LVEF and myocardial mass (systolic and diastolic) indices. Paired t-tests were used to compare the baseline scan with the follow up (6-8 week) and 12 month post treatment scan. A p value of ≤0.05 was considered significant.

Results Mean heart dose was 2.6Gy (1.5-3.9). LVEF, EDV, ESV were not significantly different 6 – 8 weeks, or 12 months following radiotherapy. LV myocardial mass index(LVMMI) (systolic), was significantly increased at 6-8 weeks follow up (53.6 vs 48.4g/m2 p<0.001) and 12 months(55.5 vs 48.4g/m2 p<0.001) following radiotherapy. LVMMI (diastolic) was significantly increased at 12 months (mean 58.5 vs 52.2g/m2 p<0.001). T1 and T2 values were not significantly elevated at the 6-8 week follow up scan , but were significantly elevated at 12 months (T1(ms) – 1213 vs 1246ms p=0.02, T2(ms) – 43.2 vs 45.7ms p<0.01). There was no change in ECV values. Detailed results can be found in Table 1.

Conclusion Preliminary results suggest that than the myocardial mass index (both systolic and diastolic) increases at 12 months following RT. T1 and T2 values were not significantly different at 6-8 weeks compared with baseline, however were increased at 12 months following radiotherapy. These results may suggest myocardial inflammation post RT occurs and may be detected utilising CMR.

Electronic Poster: Clinical track: Lung

EP-1334 Risk factors for esophagitis after hypofractionated palliative (chemo)radiotherapy for NSCLC C. Nieder 1 , K. Imingen 1 , B. Mannsåker 1 , R. Yobuta 1 , E. Haukland 1 1 Nordlandssykehuset HF, Dept. of Oncology and Palliative Medicine, Bodoe, Norway

radical radiotherapy. Material and Methods

A total of 60 patients with non-small cell lung cancer received 18F-FDG PET/CT examination prior to

Purpose or Objective