Investigations on parotid gland recovery after IMRT in head and neck tumor patients.
OBJECTIVE
in recent years, the role of intensity-modulated radiotherapy (IMRT) for head and neck irradiation has increased. The main motivation is sparing the parotid gland and reduction of xerostomia. Generally, relative parotid volumes have been evaluated for treatment outcome and planning constraints, neglecting that absolute parotid volumes can vary significantly. The aim of the present study was to investigate changes in parotid gland function and set this in relation to absolute volumes.


METHODS
46 head and neck patients were treated by sparing at least the contralateral parotid gland. The mean dose to the contralateral gland was limited to 26 Gy. Parotid function was measured with scintigraphy before and at 3, 6, 9, and 12 months after radiotherapy. Gland recovery was correlated with absolute parotid gland volumes and mean dose. Finally the dose-effect relationship was investigated.


RESULTS
the dose-volume histograms (DVHs) for the ipsi- and contralateral glands were significantly different. A correlation between absolute volumes receiving certain doses and the function loss after 3, 6, 9, and 12 months was found. The most significant correlation was found for the absolute volume that received at least 40 Gy (aV40). ED50 values of 23-38 Gy were observed for more than 50% function loss and and 52-68 Gy afor more than 75% function loss.


CONCLUSIONS
the mean dose, aV40 or aV26, revealed similar correlations with the excretion rate and with recovery. Hence, also absolute volumes can be used for treatment planning. Longer recovery times show higher ED50 values indicating partial regeneration of gland functions.
Department of Radiotherapy, Medical University Vienna, Vienna, Austria. Markus.Stock@akhwien.at
Markus
M
Stock
Wolfgang
W
Dörr
Carmen
C
Stromberger
Ulrike
U
Mock
Susanne
S
Koizar
Richard
R
Pötter
Dietmar
D
Georg
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017024:Chemotherapy, Adjuvant; D003131:Combined Modality Therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D020360:Neoadjuvant Therapy; D009367:Neoplasm Staging; D009959:Oropharyngeal Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D010306:Parotid Gland / Q000000981:diagnostic imaging* / Q000528:radiation effects* / Q000601:surgery; D011832:Radiation Injuries / Q000000981:diagnostic imaging*; D011877:Radionuclide Imaging; D011879:Radiotherapy Dosage; D018714:Radiotherapy, Adjuvant; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects*; D012472:Salivation / Q000528:radiation effects; D013670:Sodium Pertechnetate Tc 99m; D014987:Xerostomia / Q000000981:diagnostic imaging; D055815:Young Adult
D013670:Sodium Pertechnetate Tc 99m