Page 90 - Effects of radiotherapy and hyperbaric oxygen therapy on oral microcirculation Renee Helmers

Chapter 4
of 8 weeks would correspond with a period of 24 weeks (6 months) in humans and therefore would be sufficient to detect late IR injury in the microvasculature. However, the effects of RT might have manifested in a milder form in bone as damaged cells would be replaced by osteoprogenitor cells in a higher turnover rate.38 It may have been advantageous to prolong the observation period of post-IR beyond 11 weeks to determine if there may be a delayed response in the microcirculation corresponding to late IR injury as observed in human HN cancer patients.
Several points need to be considered in view of this pilot investigation. First, the small sample size per groups was very small and may not be sufficient in order to validate and ascertain adequate detection of late IR injury. Second, compared to other animal studies 11 weeks is relatively short and might therefore have been too soon to detect vascular and histology changes characteristic of late IR injury. Finally, it is difficult to scale IR doses adequately for rabbits and perhaps a higher dose may have been required in order to achieve clinically comparable tissue pathophysiology associated with mandibular IR injury.
In conclusion, the present pilot study described for the first time a model in which in vivo oral microcirculatory response after HN IR was monitored and quantified prospectively. Within the scope of this study, no significant lasting effect in terms of perfused vessel density or clinical late IR damage could be detected in the different groups after 11 weeks. In general, acute changes in vessel density and platelet counts were observed at 5 weeks after initiating IR in all groups. Marked changes in architecture (telangiectasia) and histology (loss of periosteum and vasculature) were observed after a single dose of 30 Gy. Future studies should prolong the observation period and examine injury dose-response prevalence by correlating the microcirculation, telangiectasia and histopathology findings with the progression of IR side effects.
Acknowledgements
We would like to acknowledge and thank the staff of the Department of Experimental RT for their support and Sanne Hackmann from the Animal Research Institute Academic Medical Center (ARIA) for her biotechnical support.
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