Recovery of salivary epidermal growth factor in parotid saliva following parotid sparing radiation therapy: a proof-of-principle study

Abstract

Background: Although radiation therapy (RT) causes permanent xerostomia, parotid-sparing radiation therapy (PSRT) ensures recovery of saliva quantity over time. Salivary epidermal growth factor (EGF) is produced primarily by parotid glands.

Objectives: The aim of this study was to determine whether salivary EGF can be detected in parotid saliva after PSRT and whether protein secretion is time dependent.

Study design: Salivary EGF concentration (pg/mL) was determined by enzyme-linked immunosorbent assay in stimulated parotid saliva before RT and at 3, 6, and 12 months after RT from 22 patients with head and neck cancer treated with PSRT.

Results: Saliva samples were from 17 men and 5 women (age ranges 23-70 years and 46-71 years, respectively). At 6 months after RT, EGF concentration was 407 pg/mL lower than at baseline (P = .045). Twelve months after PSRT, parotid glands produce substantial amounts of EGF and other proteins, eventually approximating pre-RT levels, with recovery of salivary function.

Conclusions: This proof-of-principle study shows that even proteins in picogram quantities, such as EGF, can be detected in saliva after PSRT.