Radiation therapy to the head and neck area can cause many side effects, including osteoradionecrosis (ORN). ORN is associated with considerable morbidity and has significant quality of life consequences for cancer survivors.rr
Definition
ORN can be defined as an area of exposed irradiated bone that does not heal over 3-6 months and is not a primary tumour, a recurrence, or a metastasis.r It is characterised by chronic necrosis and/or infection and can lead to refractory oral cutaneous fistulas, persistent exposure of bone, or pathological fracture of the mandible (jaw bone).r
Pathophysiology
The pathophysiology of ORN is multifaceted and poorly understood. Early theories suggest that ORN is caused by radiation induced endarteritis, which results in hypoxia, hypocellularity, and hypovascularity. This was based on the knowledge that dentoalveolar surgical treatments (such as dental extractions or periodontal surgery) were risk factors for the development of ORN.r Radiation causes a degree of fibrosis, thrombosis, and obliteration of the vasculature within bone, affecting its capacity to respond to injury and ultimately resulting in the necrotic process.r ORN is predominantly seen in the mandible.r The reason for this can be that the mandible has a restricted localised blood supply, which is often completely within the radiation field.r
Incidence/prevalence
The prevalence of ORN varies widely in the literature ranging from 0.4 to 56%.r More recently incidence rates have been reported as ranging from 4-8%.rr This decline is mostly credited to more conformal treatment modalities such as intensity modulated radiation therapy.rrr
Onset/duration
ORN can develop spontaneously or most commonly after dentoalveolar trauma such as dental extractions, biopsies, related cancer surgery, periodontal procedures, and mouth ulcers. The reported mean time from completion of radiation therapy to the development of osteoradionecrosis varies and ranges from 22-47 months.r
Risk factors
There are multiple risk factors for the development of ORN. These risks include patient, tumour and treatment related factors.
Patient related factors:
- pre-radiation therapy dental/tooth extractionrrand/or mandible surgeryrr
- post-radiation therapy tooth extractionrrr (one systematic review reported that the incidence rate of ORN after tooth extraction in irradiated patients was 7%)r
- tobaccor and alcohol user
- poor oral hygiene
- poor periodontal statusr
- infection from periodontal diseaserr
- co-morbidities (e.g. diabetes mellitus type 2)r
- advanced ager
- nutritional statusr
- trismusrr
Tumour related factors:
- the location of the primary tumour (tongue, floor of mouth, tonsil and retromolar trigone)
- proximity of tumour to boner
- advanced stage tumours.
Treatment related factors:
- higher doses of radiation to the jawrr
- extent of mandible included in primary radiation field
- concurrent chemotherapy.r