Table 2.
Relationship between each variable and development of ORN (univariate analysis)
| Variable | p-value | Hazard ratio | 95% confidence interval | |
|---|---|---|---|---|
| Age | 0.253 | 1.014 | 0.990–1.040 | |
| Sex | Female vs. male | 0.443 | 1.303 | 0.663–2.562 |
| Primary site | Oral cavity vs. Oropharyx | 0.750 | 0.901 | 0.473–1.713 |
| Diabetes | (−) vs. (+) | 0.947 | 1.025 | 0.495–2.122 |
| Leukocytes | 0.460 | 1.000 | 1.000–1.000 | |
| Lymphocytes | 0.566 | 1.000 | 0.999–1.001 | |
| Creatinine | 0.116 | 1.219 | 0.952–1.561 | |
| Albumin | 0.935 | 0.978 | 0.564–1.694 | |
| Total dose | 0.271 | 1.032 | 0.976–1.091 | |
| Neck dissection before RT | (−) vs. (+) | 0.297 | 0.737 | 0.415–1.309 |
| RT method | 3D-CRT vs. IMRT | 0.158 | 0.475 | 0.169–1.335 |
| Concurrent therapy | RT alone vs. CRT vs. BRT | 0.455 | 1.215 | 0.729–2.025 |
| Remaining teeth | (−) vs. (+) | 0.258 | 22.170 | 0.104–4745 |
| Alveolar bone loss | (−) vs. (+) | 0.512 | 1.215 | 0.679–2.173 |
| Periapical lesion at the start of RT | (−) vs. (+) | <0.001 | 3.714 | 2.081–6.627 |
| Severe periodontal disease at the start of RT | (−) vs. (+) | 0.007 | 2.729 | 1.317–5.653 |
| Tooth extraction before RT | (−) vs. (+) | 0.095 | 0.588 | 0.315–1.096 |
| Tooth extraction after RT | (−) vs. (+) | 0.006 | 2.536 | 1.307–4.920 |
Abbreviations: 3D-CRT: three-dimensional conformal radiotherapy; BRT: bio-radiotherapy; CRT: chemo-radiotherapy; IMRT: intensity modulated radiotherapy; ORN: osteoradionecrosis; RT: Radiotherapy.