Sparing the contralateral submandibular gland in oropharyngeal cancer patients: a planning study.
OBJECTIVE
The submandibular glands are proposed to be important in preventing xerostomia in head-and-neck cancer patients. We investigated the feasibility of sparing the contralateral submandibular gland (cSMG) by reducing the dose to the contralateral planning target volume (PTV) and by reducing the clinical target volume (CTV)-to-PTV margin.


METHODS
Ten oropharyngeal cancer patients with a contralateral elective PTV were included in this planning study, using intensity modulated radiotherapy (IMRT). The effect on the mean dose to the cSMG of reducing the dose coverage to the contralateral elective PTV from 95 to 90% of the prescribed dose (54Gy in 1.8Gy daily fractions) was determined. The influence of reducing the margin for position uncertainty from 5 to 2mm was investigated.


RESULTS
The mean dose to the cSMG was reduced from 54Gy to approximately 40Gy if the dose coverage to the contralateral PTV was reduced to 90% of the prescribed dose. The estimated normal tissue complication probability (NTCP) was reduced below 50%. Reducing the margin from 5 to 2mm resulted in a decrease in the mean dose to the cSMG of approximately 6Gy.


CONCLUSIONS
Reducing the mean dose to the cSMG below 40Gy is possible with a reasonable dose coverage of the contralateral elective PTV.
Houweling
Antonetta C
AC
Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands. A.Houweling@umcutrecht.nl
Dijkema
Tim
T
Roesink
Judith M
JM
Terhaard
Chris H J
CH
Raaijmakers
Cornelis P J
CP
D005260:Female; D006801:Humans; D008297:Male; D009367:Neoplasm Staging; D009959:Oropharyngeal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D013363:Submandibular Gland / Q000528:radiation effects*; D014057:Tomography, X-Ray Computed