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Int J Radiat Oncol Biol Phys. 2005 Jul 1;62(3):659-64.

Long-term parotid gland function after radiotherapy.

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1
Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands. P.M.Braam@azu.nl

Abstract

PURPOSE:

Irradiation of the parotid glands causes salivary dysfunction, resulting in reduced salivary flow. Recovery can be seen with time; however, long-term prospective data are lacking. The objective of this study was to analyze the long-term parotid gland function after irradiation for head-and-neck cancer.

METHODS AND MATERIALS:

A total of 52 patients with head-and-neck cancer and treated with radiotherapy (RT) were prospectively evaluated. Stimulated bilateral parotid salivary flow rates were measured before RT and 6 weeks, 6 months, 12 months, and at least 3.5 years after RT completion. A complication was defined as a stimulated parotid flow rate of <25% of the pre-RT flow rate. The normal tissue complication probability model proposed by Lyman was fit to the data. Multilevel techniques were used to model the patterns of flow rates with time.

RESULTS:

The mean stimulated flow rate of the parotid glands before RT was 0.31 mL/min (standard deviation [SD], 0.21). This was reduced to 0.14 mL/min (SD, 0.15) at 6 weeks after RT and recovered to 0.20 mL/min (SD, 0.22) at 6 months and 0.19 mL/min (SD, 0.21) at 12 months after RT. The mean stimulated flow rate was 0.25 mL/min (SD, 0.28) 5 years after RT. The mean dose to the parotid gland resulting in a 50% complication probability increased from 34 Gy at 6 weeks to 40 Gy at 6 months, 42 Gy at 12 months, and 46 Gy at 5 years after RT. Multilevel modeling indicated that both dose and time were significantly associated with the flow ratio.

CONCLUSION:

Salivary output can still recover many years after RT. At 5 years after RT, we found an increase in the salivary flow rate of approximately 32% compared with at 12 months after RT.

PMID:
15936542
DOI:
10.1016/j.ijrobp.2004.12.015
[Indexed for MEDLINE]
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