Quantification of trade-off between parotid gland sparing and planning target volume underdosages in clinically node-negative head-and-neck intensity-modulated radiotherapy.
OBJECTIVE
To quantify the trade-off between parotid gland sparing and planning target volume (PTV) underdosages for head-and-neck intensity-modulated radiotherapy.


METHODS
A planning study was performed for 4 patients with either soft palate or tonsil tumors treated with external radiotherapy up to 46 Gy. The trade-off between underdosages in the PTV and sparing of the parotid glands was investigated by systematically varying the optimization objectives for the inverse planning. A new way of presenting dose-volume information allows easy detection of small PTV subvolumes with underdosages that cannot be assessed in conventional cumulative dose-volume histograms. A simple radiobiological model to estimate the control probability for an electively irradiated neck level was developed.


RESULTS
The average dose to the parotid glands can decrease by >10 Gy by allowing the PTV to be underdosed in such a way that the radiobiological model predicts a decrease in subclinical disease control probability of (typically) 1% to a few percent.


CONCLUSIONS
The trade-off between parotid gland sparing and underdosages in the PTV has been quantified by the use of an alternative method to present dose-volume information and by the use of a radiobiological model to predict subclinical disease control probability.
de Kruijf
Wilhelmus J M
WJ
Department of Radiation Oncology, Erasmus MC-Daniël den Hoed, Rotterdam, The Netherlands. kruijf.de.w@bvi.nl
Heijmen
Ben J M
BJ
Levendag
Peter C
PC
D004307:Dose-Response Relationship, Radiation; D006801:Humans; D010157:Palatal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D010160:Palate, Soft / Q000000981:diagnostic imaging; D010306:Parotid Gland / Q000000981:diagnostic imaging; D011853:Radiobiology; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated; D014057:Tomography, X-Ray Computed; D014067:Tonsillar Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*