6th ICHNO Abstract Book

page 42 6 th ICHNO Conference International Conference on innovative approaches in Head and Neck Oncology 16 – 18 March 2017 Barcelona, Spain __________________________________________________________________________________________ patients are still alive, a 30% 2-year survival free of grade ≥3 toxicity will not be achieved. 6th ICHNO

IMAT on glottic carcinoma patients. Conventional fixed field IMRT was used as a benchmark, comparisons between CDR-CAS-IMAT and IMRT are made in the review within the areas of planning, delivery and quality assurance. Material and Methods Six patients with glottic carcinoma planning target volumes (PTVs)who were previously treated with IMRT on Varian 23EX were retrospectively planned for half arc （ C. W. from 265°to 95° ） CDR-CAS-IMAT plans, see Figure 1 and Figure 2. All plans dose prescription was set to 60 Gy to PTVs and 66 Gy to CTVs in 30 fractions. The planning objectives for PTVs and CTVs were corresponding with the IMRT plans at least 95% planning target volume reached the prescription dose and V110 no more than 10 ％ , maximum dose to spinal cord was limited to 42 Gy. Calculated dose to the PTVs and organs at risk (OAR) were compared to standard IMRT with respect to plan quality, total plan monitor units(MU), and treatment time. And delivery accuracy were analysed by delivered plan to a Delta4 phantom. Using SPSS 19.0 software paired T-test analysis two sets of data.

Results Table 1. and Table 2.shows for glottic carcinoma half arc CDR-CAS-IMAT plans have equivalent or superior plan quality as compared to IMRT. Not only can incresed the Ptv d98, ptvv95, ptvv100, and minimum dose for PTV, but also can improve homogeneity Index (HI) of PTV. The mean HI are 0.17 and 0.35 for CDR-CAS-IMAT and IMRT plans, respectively. Volumes in the cord receiving 40Gy were increased from 0.4% with IMRT to 1.4% with CDR-CAS- IMAT. And compared with IMRT plans increased the E-P low dose area. Table 3. shows treatment times were reduced significantly with CDR-CAS-IMAT(mean 69.5s vs. 223.8s, p < .05), and total plan monitor units(MU), however, increased by a factor of 1.9. There was no significant difference in γ-test and Delta4 measurements results between both planning techniques(p >0.05).

Conclusion Adaptive PET-guided reirradiation is feasible. However, due to slow accrual, the trial was stopped early. We weren’t able to evaluate the grade ≥3 toxicity rate at 2 years since poor survival was observed. PO-088 The study of constant dose rate and gantry speed arc therapy for glottic carcinoma on Varian 23EX R. Zhang 1 , Y. Gao 2 , W. Bai 1 , M. Miao 1 , D. Liu 1 1 Fourth Hospital of Hebei Medical University, Radiotherapy, Sijiazhuang- Hebei, China 2 Hebei General Hopital, Endoscopy Room, Shijiazhuang, China Purpose or Objective Volumetric-modulated arc therapy, the novel techniques during the rotating irradiation a variable dose-rate(VDR) and gantry speed is required, allowing the aperture weights to vary at different beam angles,which can only be achieved in the new accelerator and prevents most existing linacs from delivering VMAT, we propose an alternative planning approach for VMAT using constant dose-rate and gantry speed arc therapy(CDR-CAS-IMAT) implementation on conventional Linac . Planning study was performed to evaluate the performance of CDR-CAS-