Japanese Journal of Clinical Oncology Advance Access originally published online on September 28, 2006
Japanese Journal of Clinical Oncology 2006 36(10):626-631; doi:10.1093/jjco/hyl098
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© 2006 Foundation for Promotion of Cancer Research
Factors Influencing the Parotid Function in Nasopharyngeal Carcinoma Treated with Parotid-Sparing Radiotherapy
1 Department of Radiation Oncology, 2 Department of Nuclear Medicine, 3 Department of Otolaryngology, Chung Shan Medical University Hospital, Taichung, Taiwan, 4 Institute of Medicine & Toxicology, 5 Institue of Medicine, 6 Institue of Public Health, Chung Shan Medical University, Taichung, Taiwan and 7 Department of Radiation Oncology, University of California, Los Angeles, USA
For reprints and all correspondence: Wen-Shan Liu, Department of Radiation Oncology, 110, Sec. 1, Chien-Kuo N. Road, Taichung 402, Taiwan. E-mail: p53_tw{at}yahoo.com.tw
Received April 16, 2006; accepted August 11, 2006
Background: To evaluate the factors influencing post-irradiation parotid gland function in nasopharyngeal cancer treated with parotid-sparing radiotherapy.
Methods: This study consisted of 45 patients with nasopharyngeal cancer treated with radiotherapy including 3D conformal radiotherapy, intensity-modulated radiotherapy and high-dose-rate brachytherapy. The mean follow-up time was 37.5 months (range: 15–50 months). Objective parotid gland function was assessed by series sialoscintigraphy pre-irradiation and post-irradiation at 1, 6, 12 and 18 months. Subjective salivary function was recorded by the LENT/SOMA system. Wilcoxon signed-rank test was used to compare the secretion ratio (SR) of parotid gland before and after treatment. Mann–Whitney rank-sum test was used to determine the factors influencing the post-irradiated SR. Chi-square test was used to compare the correlation between subjective grading of xerostomia and objective grading of parotid glands.
Results: There was a significant difference between the pre-irradiation and post-irradiation parotid gland's SR at 1 (0.30 versus 0.01, P < 0.05) and 6 months (0.03 versus 0.08, P < 0.05). However, there was no significant difference compared with the pre-irradiation SR at 12 (0.30 versus 0.20, P > 0.05) and 18 months (0.30 versus 0.18, P > 0.05). There was significant correlation between subjective and objective salivary function (P = 0.024) at 12 months after radiotherapy. The factor that impacted the preservation of parotid function was mean dose to the parotid gland >38.0 Gy (P < 0.05).
Conclusions: Our results demonstrated that parotid function could recover 1 year after treatment with parotid-sparing radiotherapy in patients with nasopharyngeal cancer. The most important factor that influenced parotid function was the mean dose to the parotid gland.
Key Words: nasopharyngeal carcinoma • xerostomia • parotid-sparing radiotherapy • intensity-modulated radiotherapy • sialoscintigraphy