Influence of genetic background and oxidative stress response on risk of mandibular osteoradionecrosis after radiotherapy of head and neck cancer.

BACKGROUND Osteoradionecrosis (ORN) of the mandible is a severe complication of head and neck radiotherapy (RT) treatment, where the impact of individual radiosensitivity has been a suggested explanation. METHODS A cohort of patients with stage II/III ORN was compared to matched controls. Blood was collected and irradiated in vitro to study the capacity to handle radiation-induced oxidative stress. Patients were also genotyped for 8 single-nucleotide polymorphisms (SNPs) in genes involved in the oxidative stress response. RESULTS A difference in 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) levels was found between the patient cohorts (p = 0.01). The SNP rs1695 in glutathione s-transferase p1 (GSTP1) was also found to be more frequent in the patients with ORN (p = .02). Multivariate analysis of the clinical and biological factors revealed concomitant brachytherapy plus the 2 biomarkers to be significant factors which influense risk of mandibular osteoradionecrosis after radiotherapy of head and neck cancer. CONCLUSION The current study indicates that oxidative stress response contributes to individual radiosensitivity and healthy tissue damage caused by RT and may be predicted by biomarker analysis.