Does delivered OAR dose improve prediction of late toxicity in head & neck cancer patients?
Noble, D. Harrison, K. Shelley, L. E. A. Bates, A. M. Bailey, J. E. Wilson, M. Z. Romanchikova, M. Thomas, S. J. Hoole, A. Jadon, R.
Noble, D.
Harrison, K.
Shelley, L. E. A.
Bates, A. M.
Bailey, J. E.
Wilson, M. Z.
Romanchikova, M.
Thomas, S. J.
Hoole, A.
Jadon, R.
Citations
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Abstract
Purpose or Objective
Delivered radiation dose to H&N OARs (DA) may be
different from planned dose (DP), and adapting treatment
plans mid-treatment can correct for this. However, few
studies directly assess whether ART improves clinical
outcomes, and None link delivered OAR dose to side
effects. The purpose of this study was to establish whether
planned or delivered OAR dose better predicts toxicity
events, thereby providing clinical data to support ART in
HNC.
Material and Methods
198 HNC patients were treated with standard protocols on
TomoTherapy units with daily MVCT-IG. Toxicity data were
prospectively collected at baseline and 12 months. OARs manually segmented on planning CT scans were:
bilateral parotid and submandibular glands, superior and
middle pharyngeal constrictor muscles, supraglottic larynx
and oral cavity. Contours were propagated to daily MVCTs
with a specifically trained and validated open source DIR
algorithm (Elastix). Daily dose was calculated with an inhouse
ray-tracing algorithm (CheckTomo), and
accumulated to estimate delivered DVH. Planned dose was
recalculated with CheckTomo for direct comparison.
Toxicity data for the following endpoints were binarised
for analysis: CTCAEv4.03 – xerostomia, salivary duct
inflammation and dysphagia, EORTC H&N35 - dry mouth
(Q41), sticky saliva (Q42), taste disturbance (Q44),
LENT/SOM – xerostomia subjective, xerostomia
management. Forward stepwise variable selection by
likelihood ratio fed statistically significant baseline and
mean OAR DP variables (from univariate analysis) into
logistic regression based multivariate NTCP models, which
were internally validated/calibrated with 1000-fold
bootstrapping and10-fold cross-validation. The process
was repeated with mean OAR DA metrics, and DP and DAbased
model performance was compared with Nagelkerke
R2, -2 log-likelihood, discrimination slope (DS), and ROC
curve AUC statistics.
Conclusion
All models were statistically significant predictors of
toxicity. Interestingly, respective DA models had superior
Nagelkerke R2 statistics for 6/8 endpoints, 6/8 ROC curve
AUCs, and 8/8 discrimination slopes, but differences were
minimal. This may be of interest for future NTCP model
development, but supports the notion that dose deltas are
clinically insignificant in most patients, and careful case
selection is required for optimised ART.
Affiliation
Description
Date
2020
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Noble D, Harrison K, Shelley LEA, Bates AM, Bailey JE, Wilson MZ, et al. PO-0793: Does delivered OAR dose improve prediction of late toxicity in head & neck cancer patients? Radiotherapy and Oncology . 2020 Nov;152:S430–1.