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point with maximal surface distance (MSD). A validated
deformable image registration (DIR) propagated the POs
from recurrence-CT to planning-CT. The distance from POs
to the surface of the GTV was calculated and presented as
mean distance from all four POs to the GTV. The patient
specific GTV-CTV1 margin was calculated as median
surface distance from GTV to CTV1. Difference between
LRR distribution in groups with small and large CTV
margins was evaluated using Kolmogorov-Smirnov test
(p<0.05).
Results
In total 1,581 patients were identified and 297 had LRR
within the first 3 years of follow-up; of those, 172 patients
had CT-verified recurrent disease. Among them, 50% had
GTV-CTV1 margin less than 5 mm and 50% larger than 5
mm. There was no difference in sex, tumour site, stage,
tumour differentiation and p16-status between these two
groups. After successful DIR, in total 192 recurrences were
further analysed in the two margin groups; no significant
difference in LRR distribution was found (p=0.6). Of the
POs in the first and the second groups, 58% and 64%
received 95% of the prescription dose, respectively (Figure
1).
Conclusion
The presented data do not suggest any difference in
distribution of loco-regional recurrences in relation to CTV
margins. Such a difference could be expected if the CTV
margin was a key component for loco-regional recurrence
probability.
OC-0330 Locoregionally Recurrent Head and Neck
Squamous Cell Carcinoma
S.Y. Wu
1
1
Taipei Medical University Hospital, No.111- Section 3
Department of Radiation Oncology, Taipei, Chinese
Taipei
Purpose or Objective
For locoregionally recurrent head and neck squamous cell
carcinoma (HNSCC), appropriate therapeutic decisions
and prognostic factors remain unclear.
Material and Methods
The enrolled 4,839 patients were categorized into four
groups: Group 1 comprised those undergoing
chemotherapy (CT) alone; Group 2 comprised those
receiving reirradiation (re-RT) alone (total radiation dose
≥ 60 Gy through intensity modulation radiation therapy
[IMRT]); Group 3 comprised those receiving concurrent
chemoradiotherapy (CCRT) alone (irradiation total dose
≥60 Gy through IMRT); and Group 4 comprised those
receiving salvage surgery with or without RT or CT.
Results
Age ≥ 65 years, Charlson comorbidity index (CCI) score >
6, clinical stage III-IV at first diagnosis, and recurrence-
free interval < 1 year were significant independent
prognostic risk factors for overall survival as per univariate
and multivariate Cox regression analyses. After adjusting,
adjusted hazard ratios (aHRs; 95% confidence intervals
[CIs]) for overall mortality in recurrent clinical stages I and
II were 0.63 (0.45–0.89,
p
= 0.009), 0.65 (0.52–0.83,
p
<
0.001), and 0.32 (0.26–0.40,
p
< 0.001) in Groups 2, 3, and
4, respectively, whereas they were 1.23 (0.99–1.52,
p
=
0.062), 0.69 (0.60–0.79,
p
< 0.001), and 0.39 (0.34–0.44,
p
< 0.001) for Groups 2, 3, and 4, respectively, for overall
mortality in recurrent clinical stage III and IV.
Conclusion
Salvage surgery is the recommended first treatment
choice for recurrent oral cavity and pharyngeal cancers.
Re-RT alone and CCRT are more suitable for inoperable
recurrent stage I-II oral and nonoral cavity recurrent
HNSCCs, respectively.
OC-0331 Cetuximab versus Platinum-based
Chemoradiation in Locally Advanced p16 Positive
Oropharyngeal Cancer
C. Barney
1
, S. Walston
1
, P. Zamora
1
, N. Nolan
1
, V.
Diavolitsis
1
, D. Blakaj
1
, J. Wobb
1
, D. Mitchell
1
, J.
Grecula
1
, P. Savvides
2
, A. Bhatt
1
1
The Ohio State University, Radiation Oncology,
Columbus- Ohio, USA
2
The University of Arizona Cancer Center at Dignity
Health St. Joseph's Hospital, Medical Oncology, Phoenix,
USA
Purpose or Objective
Randomized trials evaluating intensity modulated
radiation therapy (IMRT) concurrent with platinum-based
chemotherapy (PBC) versus cetuximab (C225) in treating
oropharyngeal cancer (OPC) are underway but have yet to
report preliminary data. Meanwhile, as a would-be step
toward morbidity reduction, the off-trial use of C225 in
p16+ patients is increasing in frequency, even in those who
could potentially tolerate PBC. The purpose of this study
was to retrospectively compare the efficacy of PBC versus
C225 concurrent with IMRT in the treatment of locally
advanced p16+ OPC.
Material and Methods
From 2010 to 2014, 219 patients with stage III-IVB p16+
OPC were treated definitively (n=188, 6996-7000 cGy) or
postoperatively (n=31, ≥6600 cGy) with IMRT plus
concurrent PBC (n=155, Cisplatin-136 and Carboplatin-19)
or weekly C225 (n=64). Log-rank/Kaplan-Meier analysis
and Cox Regression modeling were used for univariate and
multivariate analysis (MVA) respectively.
Results
Tumor and patient characteristics were well balanced –
PBC patients had increased median follow-up time and