Osteoradionecrosis (ORN) is bone that has died as a complication of radiotherapy. It is the most serious, possible complication facing patients with oral cancer. ORN is the condition of the non-vital bone in a radiotherapy (RT) site. Most frequently, osteoradionecrosis occurs when an insult to the bone is sustained in the irradiated area, such as related, subsequent surgery or biopsy, tooth extractions or denture irritations.
Mandibular osteoradionecrosis (lower jaw) or maxillar osteoradionecrosis (upper jaw) is not in itself an infection; but it is the result of the bone’s reduced ability to heal which causes lesions, pain and fragility. Insufficient blood supply to the irradiated areas decreases the ability to heal, and any subsequent infections to the jaw can pose a huge risk to the patient.
Clinical manifestations and symptoms range from mild to severe and include:
- Reduced mobility of the jaw
- Exposed bone in the maxilla (upper jaw) and/or mandible (lower jaw)
- Bone destruction
Symptoms vary depending on the location and extent of damage to the bone. Many people do not experience any symptoms for months, even years, after the radiation treatment.
Radiation works to destroy cancerous cells through the deprivation of oxygen and vital nutrients. In the process, radiation inevitably destroys normal cells as well, by damaging small arteries and reducing circulation to the area of the mandible (lower jaw bone).
There are many factors that can contribute to the development of osteoradionecrosis. Any patient who has received 40 gray (Gy) radiation administered to the mandible is at risk, but ORN is more common in patients who have received more than 60 (Gy) radiation therapy. Since many oral cancer patients have as much as 70 Gy of radiation, they are at greater risk.
The risk of developing osteoradionecrosis is greater for those who receive a combination of both radiation and chemotherapy. The location and size of the primary tumor are other compounding factors. Other risk factors for osteoradionecrosis include the patient's immunologic and nutritional health at the time of treatment, as well as smoking at the time of treatment.
The incidence of osteoradionecrosis has greatly decreased in the last several years. Currently, the most representative study reports that 8% of patients develop the complication. Increased understanding of osteoradionecrosis, advances in radiotherapy and radiotherapy protocols, along with a multidisciplinary approach and better patient education have all played a large part in reducing the incidence.