ESTRO 36 Abstract Book

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S597 ESTRO 36 2017
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A database of HNSCC patients recruited to the Cancer
Research UK VoxTox study between March 2013 and
January 2016 was reviewed. All patients had been treated
on TomoTherapy units, according to local protocol.
Inclusion criteria for this sub-study were: full details of
treatment protocol (RT and chemo) available, adequate
follow-up, confirmed residual or loco-regionally relapsed
disease, and diagnostic quality imaging of this disease
(including MRI, PET/CT, CT) available for review. This
gave a final cohort of 12.
Imaging confirming relapse or residual disease was
uploaded to virtual simulation software (Prosoma 3.3),
where an in-built DIR package was used to fuse these
images with the planning CT and treatment dose-cube.
Residual/relapsed disease was contoured on the relapse
imaging, named rGTV, and the volume of this structure
recorded. Contours describing the 95% isodose of 65Gy,
60Gy, 55Gy and 54Gy where relevant were generated. For
each case, the proportion of rGTV covered by these
isodoses and the treatment PTV and CTVs were recorded
(labelled ‘V’). Relapses were classified according to the
95% isodose of prescription dose contour: ‘in-field’ V >
75%, ‘marginal’ V – 25-75%, ‘out of field’ V < 25%.Results
Case details are given in Table 1. Oral cavity primary
disease accounted for 15% of cases in the original cohort
available for review (prior to exclusions), but half of
patients who relapsed loco-regionally. Mean time to
relapse was 18 weeks (Std. error +/- 2.4 weeks). 10 of 12
patients (83%) had residual or relapsed disease ipsilateral
to the primary site. 2 (both lateral tongue SCCs who
underwent primary surgery followed by RT +/- chemo to
the primary site and ipsilateral neck) relapsed early (8 and
20 weeks respectively) in the contralateral, un-irradiated
neck.
Figure 1 describes the volume of rGTV covered by
pertinent isodose contours and target CTV/PTVs.
According to our criteria, 9 of 12 relapses were in-field
(75%), 1 (8.3%) was marginal and 2 (16.7%) were in
deliberately un-irradiated contralateral neck nodes as
described.Conclusion
Oral cavity tumours appeared at highest risk of relapse in
our cohort. Using DIR to map disease relapse to treatment
volumes and dose, we found most relapsed HNSCC (75%)
occurred within the high dose volume, in keeping with
previous studies, and suggesting that unfavourable biology
rather than inadequate RT is the predominant reason for
loco-regional HNSCC relapse. Our results will be used to
inform review of our neck irradiation policy, particularly
for SCCs of the oral cavity.
EP-1097 P16 expression: a predictive marker for
treatment-related outcomes in oropharyngeal cancer
patients?
A. Modesto1, T. Galissier2, A. Lusque3, E. Uro-Coste2, J.
Delord4, A. Laprie1, J. Sarini5, P. Graff1, P. Vergez5, M.
Rives1
1Institut Universitaire du Cancer, radiation therapy,
Toulouse, France
2Institut Universitaire du Cancer, Pathology, Toulouse,
France
3Institut Universitaire du Cancer, Biostatistics, Toulouse,
France
4Institut Universitaire du Cancer, Medical Oncology,
Toulouse, France
5Institut Universitaire du Cancer, Head and Neck
Surgery, Toulouse, France
Purpose or Objective
Treatment strategies in oropharyngeal squamous cell
carcinomas (OSCC) consist in either surgery followed by
adjuvant radio(chemo)therapy or definitive
radio(chemo)therapy. P16 overexpression (p16+) is
considered as a surrogate marker for HPV-induced tumors
that are associated with improved outcome whichever
treatment modality is considered in comparison with p16
negative (p16-) OSCC. To date no predictive factors are
known to guide treatment decision.
Material and Methods
All consecutive patients treated for an OSCC with a
curative intend at a single tertiary cancer center between
2009 and 2013 were eligible to this study. P16 status was
determined by immunochemistry and centrally reviewed.
Late toxicities incidence ie: dysphagia, xerostomia,
painful shoulder, osteoradionecrosis or nerve paralysis
were registrated and graded according to CTCAE v4 in
patients alive without loco-regional evolution at least 6
months after treatment completion. Three-year disease
free survival (DFS) and late severe toxicity occurrence
were compared according to p16 expression and
treatment modality: initial surgical treatment or
definitive radio(chemo)therapy.
Results
Among the 167 patients included in this study, 77 (44%)
presented a tumoral p16 overexpression (p16+). Initial