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6th ICHNO
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.
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-
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).