Long-term parotid gland function after radiotherapy

• Published in: International journal of radiation oncology, biology, physics Vol. 62; no. 3; pp. 659 - 664
• Main Authors: Braam, Pètra M., Roesink, Judith M., Moerland, Marinus A., Raaijmakers, Cornelis P.J., Schipper, Maria, Terhaard, Chris H.J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2005
• Subjects: Adult; Aged; Female; Head and Neck Neoplasms - radiotherapy; Head-and-neck cancer; Humans; Male; Middle Aged; Parotid Gland - physiopathology; Parotid Gland - radiation effects; Parotid gland function; Prospective Studies; Radiotherapy; Radiotherapy Dosage; Recovery of Function; Salivary flow; Salivation - physiology; Salivation - radiation effects; Xerostomia; Xerostomia - physiopathology; Parotid gland function; Head-and-neck cancer; Radiotherapy; Xerostomia; Salivary flow
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/j.ijrobp.2004.12.015

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.