A nomogram to predict osteoradionecrosis in oral cancer after marginal mandibulectomy and radiotherapy

Objective: There is no useful tool to clinically predict the occurrence of osteoradionecrosis (ORN) of the mandible quantitatively. The aim was to investigate the risk factors, including different modalities of radiotherapy, for developing mandibular ORN in patients undergoing marginal mandibulectomy and postoperative radiotherapy. Methods: Between January 2006 and December 2012, 167 subjects who underwent marginal mandibulectomy and postoperative radiotherapy with different modalities were enrolled. The association of ORN with mandibular bone measurements and patient variables was analyzed, and a nomogram was established. Results: Fifteen (8.98%) of the 167 patients developed ORN during the follow-up period, and ORN was significantly associated with diabetes mellitus (DM), body mass index (BMI), remaining bone height, remaining bone height to original bone height ratio, resected bone height to original bone height ratio, and mandibular dose (P: < 0.001, 0.004, 0.042, 0.018, 0.010, 0.020, respectively). Interestingly, the risk of ORN had no significant difference between conformal and intensity modulation radiation therapy (P = 0.407). Multivariate analysis revealed that DM and resected bone height to original bone height ratio ≥ 50% were independent risk factors for postoperative ORN. A nomogram consisting of BMI, DM, resected bone height to original bone height ratio, mandibulotomy, and mandibular dose for predicting the ORN-free probability was established; and the c-index of the nomogram for ORN status was 0.803. Conclusion: A nomogram based on the risk factors was plotted to strengthen the prediction of ORN quantitatively. Surgeons should be more discrete regarding the treatment plan for patients with higher probability of ORN. Level of Evidence: 3b Laryngoscope, 130:101–107, 2020.