ESTRO 2023 - Abstract Book

S378

Sunday 14 May 2023

ESTRO 2023

Conclusion In this large multi-cohort study, acute grade 3+ esophageal toxicity was increased in patients receiving concurrent chemotherapy and was consistently predicted by esophageal V35Gy and mean dose. Our results support using esophageal V35Gy or mean dose as an esophageal toxicity predictor in future trials and clinical practice. MO-0472 Prospective trial of functional lung avoidance radiation for lung cancer: quality of life report J. Lombardo 1 , E. Castillo 2 , R. Castillo 3 , R. Miller 1 , B. Jones 4 , M. Miften 4 , B. Kavanagh 4 , A. Dicker 1 , C. Boyle 1 , N. Simone 1 , M. Werner-Wasik 5 , I. Grills 6 , T. Guerrero 7 , C. Rusthoven 4 , Y. Vinogradskiy 8 1 Thomas Jefferson University, Radiation Oncology, Philadelphia, USA; 2 UT Austin, Department of Biomedical Engineering, Austin, USA; 3 Emory University School of Medicine, Radiation Oncology, Atlanta, USA; 4 University of Colorado, Radiation Oncology, Denver, USA; 5 Thomas Jefferson University , Radiation Oncology, Philadelphia, USA; 6 Beaumont Health, Radiation Oncology, Royal Oak, USA; 7 UC San Diego, Radiation Oncology , San Diego, USA; 8 Thomas Jefferson University, Radiation Oncology, Philadephia, USA Purpose or Objective A novel form of lung function imaging has been developed that uses 4DCT data to generate lung ventilation images (4DCT ventilation). Functional avoidance proposes to use 4DCT-ventilation to reduce doses to functional regions of the lung with the aim of reducing pulmonary side-effects. A 4DCT-ventilation functional avoidance, phase II, multi-center clinical trial was completed. Patient reported outcomes (PRO) are an essential measure of quality-of-life following radiotherapy. The purpose of this work is to quantify PRO changes for patients treated with functional avoidance and to compare functional avoidance PROs against historical values. Materials and Methods Patients with locally advanced lung cancer receiving curative intent radiotherapy (prescription 45-75 Gy) and chemotherapy were accrued. Each patient had a 4DCT-ventilation image generated using 4DCT data and image processing. Favorable arc geometry and optimization techniques were used to generate functional avoidance-based plans. PRO instruments included the Functional Assessment of Cancer Therapy Lung (FACT-L) questionnaire, administered pre-treatment and at 3, 6, and 12 months post-treatment to gather data on physical, social, emotional, functional, and pulmonary well-being. Based on validated methods, the FACT-TOI (Trial Outcome Index) and the FACT-LCS (Lung Cancer Subscale) metrics were calculated, and the percentage of clinically meaningful PRO declines were determined. Published PROs for lung cancer patients treated with standard thoracic chemo-radiation were taken from a co-operative group lung cancer trial (60 Gy arm of RTOG 0617) and the rate of clinically significant FACT-TOI and FACT-LCS decline was compared against patients treated with functional avoidance via the chi-square test. Results 59 patients completed baseline PRO surveys. The median age was 65, 83% of patients had non-small-cell lung cancer, with 75% having stage III disease. The median dose was 60 Gy in 30 fractions. Clinically significant FACT-TOI decline was 46.3%, 38.5%, and 26.8%, at 3, 6, and 12 months, respectively. Clinically significant FACT-LCS decline was 33.3%, 33.3%, and 29.3%, at 3, 6, and 12 months, respectively. 26.8% of patients treated with functional avoidance had a clinically significant decline at 12 months in FACT-TOI compared to 47.8% for patients treated on RTOG 0617 (p=0.029). Conclusion The current work provides an innovative combination of functional avoidance and PROs and is the first report of patient report outcomes for patients treated on a prospective 4DCT-ventilation functional avoidance trial. Approximately 30% of patients had a clinically significant decline in PROs that persisted at 12 months. These results compare favorably to outcomes after standard thoracic chemo-radiation in RTOG 0617, where a decline at 12 months persisted in approximately half the patients. The study provides further evidence for improved outcomes with 4DCT-ventilation functional avoidance. MO-0473 Lymphopenia during NSCLC ChemoRT is proportional to FLT-detected suppression of irradiated marrow M. MacManus 1 , E. Prinz 1 , F. Hegi-Johnson 1 , J. Callahan 2 , R. Hicks 2 , T. Akhurst 2 , S. Xie 3 , S. Everitt 1 1 Peter MacCallum Cancer Centre, Radiation Oncology, Melbourne, Australia; 2 Peter MacCallum Cancer Centre, Molecular Imaging, Melbourne, Australia; 3 Peter MacCallum Cancer Centre, Biostatistics and Clinical Trials, Melbourne, Australia Purpose or Objective Adjuvant immunotherapy improves survival after chemoradiotherapy (chemoRT) in advanced non-small-cell lung cancer (NSCLC) but immunotherapy requires a functioning immune system. Bone marrow is exquisitely sensitive to radiation and lymphopenia is common after chemoRT. The potential association between loss of proliferating irradiated bone marrow and cytopenias during chemoRT has not been reported in NSCLC. We used serial 18F-fluorothymidine (FLT) PET scans to quantify loss of proliferating bone marrow during chemoRT (upper figure) and correlated bone marrow ablation with changes in circulating lymphocyte counts. Materials and Methods We conducted a retrospective analysis of FLT-PET scans from a prospective observational trial of serial PET imaging in NSCLC patients treated with chemoRT to 60 Gy. Of 60 enrolled patients, complete data for FLT-PET scans at baseline and weeks 2 and 4 were available for 28. The bony skeleton was auto-segmented in MIM software enabling FLT uptake in bone marrow to be quantified. The percentage of total injected FLT delivered to bone marrow provided a baseline value. Based on quantitative dose response analyses (data reported in a companion abstract), volumes of bone marrow exposed to >3 Gy at weeks 2 and 4 were considered to have no FLT-PET-detectable marrow proliferation. The percentage of the total injected dose of FLT missing from the bone marrow in the volume irradiated to >3 Gy was estimated by comparing 3 Gy isodose volumes at weeks 2 and 4 with the baseline scan. Changes in lymphocyte nadir (lowest value) in periods from baseline to week 2 and baseline to week 4 were analysed. Lymphocyte counts were normalised, assuming the baseline to be 0%. Estimated percentage losses of marrow from baseline to weeks 2 and 4 were correlated with % loss of lymphocyte counts during the same periods.