Risk Factors for Recurrence of Ameloblastoma: a Long-term Follow-up Retrospective Study

Ameloblastoma is a benign odontogenic tumour showing locally aggressive characteristics. This retrospective study was performed to investigate the long-term treatment outcomes of ameloblastoma and to evaluate the risk factors for recurrence. The study was conducted in the Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, the University of Hong Kong and covered the years 1990-2017. Patient demographic data, radiographic pattern and findings, clinical findings, tumour site and size, World Health Organization classification, treatment modality, histological pattern, duration of follow-up, and timing of recurrence were recorded and analyzed. The potential risk factors were analyzed by Kaplan-Meier and Cox regression tests. The cases of a total of 128 patients were reviewed; 65 were male and 63 were female. The mean follow-up period was 117 months. The 5-, 10-, and 15-year recurrence rates were 9.3%, 17.6%, and 24.4%, respectively. Kaplan-Meier and Cox regression tests showed that recurrence was significantly associated with radiographic pattern, tumour size, and treatment modality. Multiple regression analysis for these three variables demonstrated that treatment modality was the only independent prognostic factor for recurrence. This study showed that radical resection is the only significant factor for a low recurrence rate of ameloblastoma and patients require long-term follow-up for late-onset recurrence.