ESTRO 38 Abstract book

S728 ESTRO 38

EP-1328 A comparison of voluntary vs ABC breath hold in combination with VMAT for pan lymph node breast RT A. Ranger 1 , A. Dunlop 1 , E. Donovan 2 , E. Harris 1 , N. DeSouza 1 , H. McNair 1 , A. Kirby 1 1 ICR and Royal Marsden NHS Foundation Trust, Clinical Oncology, Sutton, United Kingdom ; 2 University of Surrey, Centre for Vision Speech and Signal Processing, Guildford, United Kingdom Purpose or Objective Breath holding techniques reduce radiation dose to the heart for patients undergoing locoregional breast radiotherapy. This can be achieved either by using machine assisted techniques or voluntary breath hold with no apparent difference in reproducibility between techniques in the context of tangential treatments for the breast/ chest wall. This study aimed to compare the reproducibility of volumetric modulated arc therapy (VMAT) in combination with vDIBH to VMAT in combination with the active breathing co-ordinator (ABC™, Elekta, Crawley, UK) device. We also aimed to test the feasibility of delivering radiotherapy using vDIBH in combination with VMAT and to patients who require wax bolus for treatment. Material and Methods Patients requiring locoregional breast radiotherapy including the internal mammary chain (IMC) either with wax bolus or with the combination of VMAT in breath hold were scanned in vDIBH and using the ABC device. Patients were randomised to receive one technique for fractions 1- 7 and the other for fractions 8-15. Daily cone beam computer tomography (CBCT) was performed and matched to planning-CT data. Within patient comparisons of mean daily chest wall position were made using a paired t- test. Estimates of population, systematic and random errors were also made. Diaphragm positions in consecutive breath holds were measured and compared between techniques using the Wilcoxon signed-rank test. A novel couch mounted laser was developed to enable the use of vDIBH in combination with VMAT and for patients requiring wax bolus during treatment. Acute skin, lung and oesophageal toxicity was also recorded during and two weeks post treatment. Results 16 patients completed treatment using both techniques. There was no statistically significant difference in mean chest wall displacement between techniques in any direction (≤ -1.3mm for ABC, ≤ -1.5mm for vDIBH, all p non-significant). There was no difference in diaphragm position in consecutive breath holds between techniques (p=0.30, Figure 1) and treatment times were equivalent.

Results for acute skin toxicity according to RTOG criteria, acute lung and oesophageal toxicity according to CTCAE criteria during the third week of radiotherapy and two weeks post treatment are presented in table 1. There was no grade 3 or 4 toxicity reported.

2 weeks post treatment(% of patients)

On treatment(% of patients)

Toxicity

Grade 0 Grade 1 Grade 2 Grade 0 Grade 1 Grade 2 Grade 0 Grade 1 Grade 2

33 77 0

31 46 23

Skin

87 0 13

77 0 23

Pneumonitis

92 0 8

53 0 47

Oesophagitis

Conclusion This study demonstrates that it is feasible to use vDIBH in combination with wax bolus or VMAT therapy for the treatment of breast cancer patients. Results support previous data that ABC and vDIBH are comparable in terms if positional reproducibility. EP-1329 A Single Pre-Operative Radiation Therapy (SPORT) Phase 1 Trial For Low Risk Breast Cancer C. Pembroke 1 , M. Yassa 2 , C. Lambert 3 , V. Panet- Raymond 3 , S. Meterissian 4 , F. Trembley 4 , D. Anderson 5 , P. Vavassis 6 , T. Hijal 3 1 Velindre Cancer Centre, Clinical Oncology, cardiff, United Kingdom ; 2 University of Montreal, Radiation Oncology, Montreal, Canada ; 3 McGill University Health Centre, Radiation Oncology, Montreal, Canada ; 4 McGill University Health Centre, Surgery, Montreal, Canada ; 5 McGill University, Surgery, Montreal, Canada ; 6 University of Montreal, Surgery, Montreal, Canada Purpose or Objective A single-arm phase 1 feasibility trial offering a preoperative 20Gy fraction for low-risk breast cancer in the post-menopausal setting. We report on our primary objective; feasibility, surgical and cosmetic toxicity at 3 months. Material and Methods Eligibility criteria for low-risk disease included, age ³60 years, unifocal invasive ductal carcinomas <2cm, clinically

Patients were successfully treated using VMAT in vDIBH including eleven who required wax bolus. Figure 2 demonstrates the use of the couch mounted laser.