608 / 1096
S592
ESTRO 36
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Radiation Oncology - Oncology and Hemato-oncology,
Milan, Italy
Purpose or Objective
To explore dosimetric predictors of acute dysphagia in
head and neck (H&N) cancer patients (pts) treated with
definitive radiotherapy (RT). We prospectively examined
correlation between doses to swallowing-associated
structures and acute radiation-related side effects, in
terms of dysphagia and percutaneous endoscopic
gastrostomy tube (PEG) requirement.
Material and Methods
We analyzed all consecutive not previously treated pts
with H&N cancer who underwent RT at our Department
between May 2010 and March 2011. Exclusion criteria
were: baseline dysphagia (functional dysphagia or enteral
nutrition) and previous surgery in the H&N region. A
nutritional standardized step-wedge protocol was applied.
Dysphagia (grade ≥3 according to CTCAE v4.0) and
indication to PEG insertion were classified as acute
toxicity events. Ten swallowing-related structures were
considered for the analysis: pharyngeal axis, base of
tongue, constrictor muscles (superior, middle and
inferior), cricopharyngeal muscle, soft palate, cervical
esophagus, oral cavity and supraglottic larynx. Dosimetric
parameters included mean dose (Dmean), near maximum
dose (D2%) and the percentage volume exceeding X Gy
(Vx) evaluated in 5-Gy steps. The correlation of clinical
information along with swallowing-related structure dose
parameters related to acute toxicity events was analyzed
by means of Spearman’s rank correlation coefficient (Rs).
Multivariate logistic regression method using resampling
methods (bootstrapping) was applied to select model
order and parameters for normal tissue complication
probability (NTCP) modeling. Model performance was
evaluated through the area under the curve (AUC) of the
receiver operating characteristic (ROC) analysis.
Results
Patient and treatment characteristics are summarized in
Table 1. Two pts required PEG, 3 pts had grade 3
dysphagia and 4 pts had both PEG and grade 3 dysphagia.
A strong multiple correlation between dosimetric
parameters was found. Intra-organ dosimetric parameters
were strongly correlated as well as inter-organ dosimetric
parameters. Accordingly, the highly correlated variables
(Rs>0.75) were not included in the multivariate analysis.
A two-variable model was suggested as the optimal order
by bootstrap method. The optimal model (Rs=0.452,
p<0.001) includes V45 of the cervical esophagus
(OR=1.016) and Dmean of the cricopharyngeal muscle
(OR=1.057). The model AUC (Fig1a) was 0.82 (95% CI 0.69-
0.95). The comparison of the predicted incidence of acute
radiation-related toxcity and the actuarial incidence in
the
population
is
shown
in
Figure
1b.
Conclusion
We propose a 2-variable predictive NTCP model including
both cervical esophagus and cricopharyngeal muscle
dosimetric parameters with a good prediction
performance for acute radiation-related toxicity in H&N
cancer pts
EP-1078 Transient xerostomia in head and neck
cancers with significant parotid inclusion in target
volume
A. Datta
1
, A. Mukherji
1
, E. Thiraviyam
1
1
Jawaharlal institute of post graduate medical education
and research, radiation oncology, Puducherry, India