ESTRO 2020 Abstract Book

S541 ESTRO 2020

PO-1014 Mitigating breathing motion with nasal high flow therapy (NHFT) in lung cancer: A prospective study S. Peeters 1 , S. Canisius 1 , D. Tissen 1 , E. Van Enckevort 1 , E. Rousch 1 , M. Öllers 1 , G. Bosmans 1 , K. Verhoeven 1 , C. Overhof 1 , J. Van Loon 1 , D. De Ruysscher 1 , G. Vilches- Freixas 1 1 MAASTRO Clinic, Radiation Oncology, Maastricht, The Netherlands Purpose or Objective Reducing breathing motion in RT is an attractive strategy to reduce margins, to better spare normal tissues. Also proton RT might benefit from this, as anatomical shifts caused by breathing can lead to severe over- and underdosage. The objective of this prospective study is to investigate the feasibility of treating NSCLC patients in moderate deep inspiration breath hold (mDIBH) using a nasal high-flow therapy (NHFT) device in order to mitigate the breathing motion. Material and Methods Stage III NSCLC patients were prospectively included and treated with photon RT during mDIBH using a NHFT device (AIRVO ® ). This device administers heated humidified air (flow 40 l/min, 80% O2) through a nasal interface. The breath hold (BH) with visual feedback through goggles was monitored by optical surface scanning (C-RAD ® ), with a gating window of 3mm. During training session patients were instructed to hold their breath as long as possible, 2x without (BH_w/o), and 2x with NHFT (BH_NHFT); the maximum BH length is reported. PlanningCT and treatment were done in mDIBH; a back-up plan in free breathing (FB) was available. Every session, matching was performed through a CBCT in BH. During treatment, patients were instructed to keep the BH as long as they wish; the beam delivery was automatically gated with the breathing signal. Subjective tolerance was measured with a questionnaire (5-points scale: 0 (no) to 5 (maximal discomfort)) at training session, first and last treatment fraction. Results Nine patients were included (5 males/4 females). Mean age was 68 years (range 60-74y). Mean FEV1 was 63% (Fig1). Five patients had concurrent chemoRT (60Gy/2Gy). One patient was excluded after training session because of metastatic disease on planningCT. Six out of 8 patients (75%) completed the whole treatment as planned. Two patients asked for a FB back-up treatment for 2 and 3 fractions, at a dose of 40Gy and 54Gy, respectively, because of bad condition due to side effects caused by chemoRT. At the training session, the mean length of BH_w/o was 43s (range 15-85s;SD 21s), and of BH_NHFT 106s (range 32-220s;SD 62s) (Fig1). With NHFT, the BH duration was significantly prolonged by a mean factor of 3.0 (range 1.1-9.2;SD 2.7)(p=0.02). The mean session time from entering to leaving the room was 23min (SD 2,7) . The length of the BHs during the treatment sessions (mean 48s, SD 15s) allowed performing the CBCT in one BH for all patients and, for some, to deliver more than one beam in one BH . Subjective tolerance was very good (Fig2).

Conclusion Compared to a breath hold without any support, NHFT significantly increased the duration of a BH by a factor 3 (from 43 sec to 106 sec) during the training session. 75% of treated NSCLC patients were able to tolerate the irradiation in breath hold with NHFT for the whole treatment. Subjective tolerance of the device was excellent. This device offers a promising solution to treat lung cancer patients in BH both for photon and proton RT. PO-1015 SBRT after CT-RT for stage III unresectable NSCLC with peripheral primary tumor (GFPC 01-14 study) I. Martel-Lafay 1 , S. Danhier 2 , E. Blanc 3 , I. Monnet 4 , O. Gallocher 5 , N. Salem 6 , H. Berard 7 , O. Bykicki 8 1 Centre Léon Bérard, Radiation Therapy Department, Lyon, France ; 2 Centre François Baclesse, Radiation Therapy Department, Caen, France ; 3 Centre Léon Bérard, Clinical Research and Statistics Department, Lyon, France ; 4 Centre Hospitalier Intercommunal, Chest Department, Créteil, France ; 5 Clinique Pasteur, Radiation Therapy Department, Toulouse, France ; 6 Institut Paoli Calmette, Radiation Therapy Department, Marseille, France ; 7 HIA Saint Anne, Chest Department, Toulon, France ; 8 HIA Percy, Chest Department, Clamart, France Purpose or Objective Concurrent chemoradiation (CCRT) is the standard treatment for unresectable stage III NSCLC. When considering stage III pts presenting with a peripheral primary tumor, irradiated volume may include a large part of normal lung, which could result in severe radiation pneumonitis. SBRT is known to provide excellent control rates in early stage NSCLC. In this study, we evaluated the feasibility of delivering SBRT to the primary tumor, after CCRT for nodal hilar or mediastinal involvement, with the aim of minimizing the risk of severe radiation toxicity.