Osteoradionecrosis (ORN) of the Mandible in Head/Neck Cancer Treated with Intensity Modulated Radiation Therapy (IMRT)

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Retrospective review of the incidence and patterns of ORN in head/neck cancer patients treated with IMRT at a single institution. We combined our institutional databases of head/neck cancer patients who underwent IMRT from 9/99 to 5/07 (n = 218). The sites were: nasopharynx (n = 25), paranasal sinuses (n = 35), oral cavity (n = 36), oropharynx (n = 41), larynx/hypopharynx (n = 31), and thyroid gland (n = 50). The T-stages were: T1, 9% (n = 19); T2, 28% (n = 61); T3, 19% (n = 42); T4, 41% (n = 89). Seven patients were not staged. Fifty-four percent of patients (n = 118) underwent surgery prior to RT and 57% (n = 125) had chemotherapy as a component of their initial treatment. Six patients (3%) had mandibular invasion prior to treatment. All patients underwent a comprehensive dental examination at our institution and were given instructions on post-RT dental care/fluoride treatment. Patients that were expected to receive a significant dose to the oral cavity were also fitted with a mouth guard prior to treatment. Pre-RT extractions were performed in 15% of patients (n = 33). The median prescription dose was 69.96 Gy. The median Dmax, mean dose, D05, and D95 doses were 66.89 Gy (range, 24.71-77.69 Gy); 37.46 Gy (range, 3.36-65.30 Gy), 60.09 Gy (range, 16.76-73.32 Gy), and 15.99 Gy (range, .29-56.85 Gy), respectively. The mean mandibular volume receiving IMRT was 73 cc (range, 8-163 cc). Median doses to the left and right parotid gland were 25.61 Gy (range, .90-65.95 Gy) and 25.54 Gy (range, .53-59.07 Gy), respectively. With a median follow-up of 28 months (range, 1-101 months), 2 patients, both with oral cavity primaries, (stages T2N2 and T2N1) experienced ORN. The first patient had ORN 31 months after IMRT. He underwent a sequestrectomy and had healed well at last follow-up. The second patient had ORN 32 months after IMRT. He underwent surgical debridement and also healed fully at last follow-up. In addition to surgery, these patients also underwent post-operative concurrent chemoradiotherapy. Neither patient had mandibular invasion prior to treatment. The mandibular and parotid parameters in these 2 patients were: Dmax, 68.28/71.83 Gy, mean dose 53.35/58.12 Gy, D05 64.64/70.17 Gy, D95 14.98/28.30 Gy, volume 66.8/87 cc, left parotid 25.99/24.73 Gy, and right parotid 23.95/25.30 Gy, respectively. ORN is rare after treatment of head/neck cancer with IMRT. However, the incidence was 6% in oral cavity cancer. Due to the delayed onset of this complication more patients may experience ORN with longer follow-up. Patients that experienced ORN had mandibular parameters that were higher than the median values. All patients should be followed with rigorous dental care and mandibular dose constraints should be applied.