ESTRO 2021 Abstract Book

S999

ESTRO 2021

We performed a retrospective analysis of consecutive patients undergoing passive scattering PBT for histologically or clinically diagnosed Stage I and lymph-node negative Stage IIA NSCLC according to the 7th edition of the Union for International Cancer Control TNM classification between January 2004 and December 2016. Patients with synchronous or metachronous malignancies within 3 years from the first day of PBT were excluded from analysis. Overall survival (OS), progression free survival (PFS), and local progression-free (LPF) rates were estimated using Kaplan–Meier analysis. Survival distribution was compared between groups using log-rank tests. The first site of failure was classified as local failure, regional lymph node (LN) failure, or distant metastasis (DM). Statistical analyses were performed using JMP version 13 (SAS Institute, Cary, NC). Results A total of 179 patients were assessable for this analysis (136 men [76.0%]; median age, 77 [range 41-89] years). NSCLC was confirmed histologically in 149 patients (83.3%), and 113 (63.1%), 51 (28.5%), and 15 (8.4%) patients were classified as Stage IA, IB, and IIA, respectively. The median biological effective dose (BED) delivered for all patients was 112 GyE (range 80.5–131.3 GyE). The median BED delivered for patients with Stage IA, IB, and IIA disease was 109.6 GyE (range 80.5–131.3 GyE), 112 GyE (range 87.5–131.3 GyE), and 105.6 GyE (range 86.0–112 GyE), respectively. The median follow-up period was 34.5 months (range 0.5–155 months) for all patients and 44.5 months (range 0.5–155 months) for surviving patients. The 3-year OS, PFS, and LPF rates for all patients were 71.1%, 57.7%, and 84.0%, respectively. For patients with Stage IA, IB, and IIA disease, the 3-year OS rates were 76.9%, 64.4%, and 52.5%, respectively (P = 0.0003); the 3-year PFS rates were 66.9%, 47.9%, and 22.2%, respectively (P = 0.0001); and the 3-year LPF rates were 86.3%, 82.3%, and 70.7%, respectively (P = 0.057). Local failure, regional LN failure, and DM were observed as the first failure site in 11 (9.7%), 16 (14.2%), and 22 (19.5%) Stage IA patients, respectively ; in 9 (17.6%), 7 (13.8%), and 10 (19.6%) Stage IB patients, respectively; and in 3 (20.0%), 6 (40.0%), and 7 (46.7%) Stage IIA patients, respectively. The incidence of Grade 2, 3, 4, and 5 radiation pneumonitis was 10.1%, 0%, 0.6%, and 0.6%, respectively. Conclusion Although PBT is an effective treatment for Stage I and lymph node-negative IIA NSCLC, regional LN failure and/or DM were common first failure sites for patients with Stage IIA disease. Systemic chemotherapy may have a possible role in these patients. PO-1203 lung-perfusion-spect contribution in lung cancer radiotherapy planning process S. Baroni 1 , I. Dell'Oca 2 , R. Tummineri 2 , A. Sanchez Galvan 3 , F. Borroni 2 , S.L. Villa 3 , G. Mandurino 3 , P. Pacifico 3 , A. Chiara 2 , M. Pasetti 2 , N. Slim 2 , E.G. Vanoli 4 , A. Del Vecchio 5 , S. Arcangeli 6 , N.G. Di Muzio 7 1 IRCCS San Raffaele Scientific Institute, University of Milano-Bicocca, Radiadion Oncology, Milan, Italy; 2 IRCCS San Raffaele Scientific Institute, Radiation Oncology, Milan, Italy; 3 IRCCS San Raffaele Scientific Institute, University of Milano-Bicocca, Radiation Oncology, Milan, Italy; 4 IRCCS San Raffaele Scientific Institute, Nuclear Medicine, Milan, Italy; 5 IRCCS San Raffaele Scientific Institute, Medical Physics, Milan, Italy; 6 University of Milano-Bicocca, Radiation Oncology, Milan, Italy; 7 IRCCS San Raffaele Scientific Institute, Vita e Salute University, Radiation Oncology, Milan, Italy Purpose or Objective Aims: Lung cancer radiotherapy (RT) is associated with potential risk of serious lung injury due to vascular damage. Lung Perfusion can be considered a new parameter to avoid lung toxicity in RT treatment. The inclusion of Lung Perfusion SPECT (L-P-SPECT) information in the planning process could be useful to better spare normal functional lung tissue (FLT) switching from an anatomical to functional base planning. Materials and Methods Methods: From March 2017 to December 2018, 41 patients (pts) (16 women, 25 men) with lung cancer and 47 lesions were treated with Tomotherapy (Accuray Inc, Madison, WI; TT). Thirty-eight pts had I-IIIB stage NSCLC (26 adenocarcinoma (adk), 8 squamous cell carcinoma, 1 Large cell carcinoma, 3 PET+ lesions NOS) and 3 pts had lung metastasis; 28 pts had central cancer whereas 13 pts had periferic lesion. All pts underwent L-P- SPECT and PET before TT. According to the literature, FLT was defined as two volumes with a cut-off of 20% (T20) and 30% (T30) perfusion threshold. Median PTV was 174 cc (25cc-567cc), median BTV was 11 cc (1cc- 175cc). In 21 pts (51%) PTV also included mediastinum. V5, V10, V20 and mean dose were evaluated for whole and unilateral lung considering parameters of T20, T30. 23 pts (56%) were treated with conventional fractionation, median delivered dose was 60 Gy (60-70Gy) (1,8-2,0 Gy/fr); 18 pts (44%) received hypofractionated TT, median delivered dose was 60 Gy (2.65-9 Gy/fr in 6-25 fr). Toxicity was assessed by CTCAE 4.0 criteria. Results Results: 34 pts (83%) showed G0 acute toxicity; 5 (12%) pts reported G1-G2 toxicity (cough 68% and dyspnea 62%). Two chemo pretreated pts (5%) (1: CBDA + Pemetrexed 1: CDDP) had G3 acute toxicity (bacterial pneumonia) resolved with antibiotic drugs. A G3 late toxicity (bilateral interstitial pneumonia) was registered six months after the end of TT, probably related to immunotherapy started 4 months before. V5, V10, V20, mean dose were similar in FLT and in whole lung. Conclusion Conclusions: Despite more than half of pts received the radiation on mediastinum and despite the median PTV volume was considerable (174cc) we registered only one G3 late lung toxicity. In our experience, L-P-SPECT can be included in the planning process in order to reduce significantly lung toxicity. The next step will be try to find a specific constraint for FLT allowing the full implementation in the plan optimization together with respiratory function tests. PO-1204 Adjuvant immunotherapy after concurrent chemoradiotherapy for stage 3 NSCLC, outcomes from a large cancer centre F. Sun 1 , H. Mason 1 , K. Franks 1 , M. Teo 1 , P. Dickinson 1 , K. Clarke 1 , P. Jain 1 1 Leeds Teaching Hospitals, Oncology, Leeds, United Kingdom