Infected osteoradionecrosis of the mandible: follow-up study suggests deterioration in outcome for patients with Actinomyces-positive bone biopsies.

Infected osteoradionecrosis (IORN) is one of the major complications of oral cancer radiotherapy. Recent studies showed a high prevalence of Actinomyces in IORN. In this study, the clinical follow up of IORN patients (n=25; 20 male, 5 female) with regard to Actinomyces detection in the mandible was analyzed. Within 1.6-119 months of follow up, disease control was achieved in almost 90% of the patients with Actinomyces-negative bone biopsies, but only in 25% of the Actinomyces-positive group. The presence of Actinomyces was associated with a significantly higher risk of treatment failure (P=0.004; Fisher's exact test). This held true when the data were controlled for 'extent of bone destruction', 'type of surgery' and 'soft-tissue closure' in a logistic regression analysis (P=0.018; Wald test). Since Actinomyces was detected in a significant number of patients with non-healing mucosal defects, this microbe may promote the persistence of chronic non-healing inflammatory processes. Actinomyces positivity defines a subpopulation with a clinically deteriorated course of mandibular IORN.