Parotid gland-sparing 3-dimensional conformal radiotherapy results in less severe dry mouth in nasopharyngeal cancer patients: a dosimetric and clinical comparison with conventional radiotherapy.
OBJECTIVE
This study examined the efficacy of parotid gland sparing of three-dimensional conformal radiotherapy (3DCRT) compared with conventional radiotherapy for NPC patients. Both the dose given to the parotids and clinical assessment of dry mouth were conducted.


METHODS
Dry mouth was assessed for 108 patients treated with conventional technique and 72 treated with 3DCRT. Dose analysis was performed in 48 patients of the 3DCRT group. A dose of 70 Gy was given to the midplane in conventional radiotherapy and to 90% isodose volume in 3DCRT. Prognostic factors affecting the severity of dry mouth were analyzed using Generalized Estimating Equation (GEE).


RESULTS
In the 3DCRT group about 50% of the patients' parotid glands received less than 25 Gy. Parallel analysis of dry mouth shows a significant decrease in the incidence of severe xerostomia after 3DCRT. The proportion of patients without dry mouth was also significantly higher in the 3DCRT group than the conventional group at 1-3 years after completion of radiotherapy. Although 3DCRT delivered a higher dose to the tumor, it spared the parotid gland significantly better than the conventional treatment. Late toxicities were mostly similar between the 2 groups while local control in T4 patients and survival were improved for 3DCRT.


CONCLUSIONS
Dosimetrically and clinically 3DCRT is better than conventional technique regarding parotid gland protection.
Jen
Yee-Min
YM
Department of Radiation Oncology, Tri-Service General Hospital, Taiwan, ROC. yeeminjen@yahoo.com.tw
Shih
Rompin
R
Lin
Yaoh-Shiang
YS
Su
Wan-Fu
WF
Ku
Chih-Hung
CH
Chang
Chiou-Shiung
CS
Shueng
Pei-Wei
PW
Hwang
Jing-Min
JM
Liu
Dai-Wei
DW
Chao
Hsing-Lung
HL
Lin
Hon-Yi
HY
Chang
Li-Ping
LP
Shum
Weng-Yoon
WY
Lin
Chun-Shu
CS
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D010306:Parotid Gland / Q000528:radiation effects*; D011832:Radiation Injuries / Q000517:prevention & control*; D020266:Radiotherapy, Conformal / Q000379:methods*; D014987:Xerostomia / Q000209:etiology* / Q000517:prevention & control*