The impact of intensity-modulated radiation treatment on dento-alveolar microvasculature in pharyngeal cancer implant patients.

Abstract

Dental rehabilitation post-radiotherapy often requires the consideration of dental implants. However, these are tentatively prescribed due to the concern of hypovascularisation and possible osteoradionecrosis. Hence, the current study assessed the microvasculature of the dento-alveolar bone at implant sites taking into consideration the exact radiotherapy dose received to the region. Bone cores were taken from nine patients during implant treatment and compared to nine control patients. Specimens were stained using CD31 and digitalised using a high-resolution scanner for qualitative and quantitative assessment of the microvasculature. Monaco® treatment planning system was used to volume the implant site providing mean dose (Dmean ) and maximum dose (Dmax ). A total of 23 bone cores were retrieved for analysis. The cohort had a Dmean of 38.4Gy (59.6-24.3Gy). Qualitative analysis identified a clear reduction in the miniscule terminal capillaries and high incidence of obliterated lumens with increasing radiotherapy. Microvasculature density of irradiated patients was markedly reduced (P=.0034) compared to the control group with an inverse correlation to RT doses (P<.0001). Specifically, doses up to 30Gy appear to preserve sufficient vascularisation (~77% in comparison with control) and tissue architecture. By contrast, exposure to higher doses 40%-61% of the micro-vessels were lost. Intensity-modulated radiotherapy doses above 30Gy identified reduction in microvasculature which is a lower threshold than previously accepted. In pharyngeal cancer patients' doses to the jaw bones often exceed this threshold. Coupled with favourable survival in certain oropharyngeal and nasopharyngeal cancer, dental rehabilitation via implants provides a significant clinical challenge.