Esophageal wall dose-surface maps do not improve the predictive performance of a multivariable NTCP model for acute esophageal toxicity in advanced stage NSCLC patients treated with intensity-modulated (chemo-)radiotherapy

In our previous work, a multivariable normal-tissue complication probability (NTCP) model for acute esophageal toxicity (AET) Grade ≥2 after highly conformal (chemo-)radiotherapy for non-small cell lung cancer (NSCLC) was developed using clinical parameters and mean esophageal dose (MED). Since the esophagus is a tubular organ, spatial information of the esophageal wall dose distribution may be important in predicting AET. We investigated whether the incorporation of esophageal wall dose-surface data with spatial information improves the predictive power of our NTCP model. For 149 NSCLC patients treated with highly conformal radiation therapy esophageal wall dose-surface histograms (DSHs) and polar dose-surface maps (DSMs) were generated. DSMs were used to generate new DSHs and dose-length-histograms (DLHs) that incorporate spatial information of the dose-surface distribution. Following our previous work, new multivariable NTCP models were developed using histogram derived parameters. Univariate logistic regression analysis showed that these histogram parameters correlated significantly with AET. However, incorporation of esophageal wall dose-surface data with spatial information did not improve the predictive performance of the established multivariable NTCP model based on conventional dose-volume data. For prediction of AET spatial information of the esophageal wall dose distribution is of no added value and it is sufficient to only consider MED as a predictive dosimetric parameter.