Page 117 - Effects of radiotherapy and hyperbaric oxygen therapy on oral microcirculation Renee Helmers

Effects of HBOT on late irradiation injury
INTRODUCTION
Late radiation tissue injury (LRTI) is an inevitable and potentially progressive side effect that becomes clinically apparent after 6 months to years and is associated with radiotherapy (RT) in the treatment of cancer. Tissue hypoxia that results from RT-induced vascular hypoperfusion has a negative effect on the quality of tissue and prevents an adequate healing response after tissue injury or elicits spontaneous breakdown. This can ultimately lead to necrosis of bone, cartilage and soft tissues which are difficult to treat conditions. Consequently, functional and aesthetic problems can arise that have a major impact on quality of life.7,16 It is difficult to make a prediction on whether and when late irradiation (IR) side effects will occur and evolve to clinical pathology as the degree of acute effects does not correlate with the severity of late effects.5,23,39 However, fraction dose and individual patient related factors are identified as potential risk factors.8,21,30 The underlying detrimental effects of LRTI only become clinically evident when tissue breakdown occurs with no tendency to heal.
Hyperbaric oxygen therapy (HBOT) is directed at improving IR tissue
quality by increasing oxygen tension in hypovascular tissues to promote neoangiogenesis.10,18 Although several studies show beneficial effects of
HBOT on IR HN tissue, the mechanisms remain largely elusive and very limited
evidence for preventing and managing ORN exists.4,26 However, administering
HBOT is often used curatively or prophylactically in IR tissues and the existing 6 treatment protocols are still based on research performed in the 1970s.26 In
2019 the first randomized controlled trial was published in the HN region in which data based on 100 patients showed a low occurrence rate of mandibular ORN 6 months after dentoalveolar surgery in both the HBOT group and the control group (6.4 % vs. 5.7 %); such results would not justify an indication of HBOT to prevent ORN after dentoalveolar surgery. However, it remains uncertain whether iatrogenic trauma causes or accelerates tissue breakdown that would otherwise emerge on the long-term due to poor tissue quality as a result of IR.25
Microcirculation monitoring can give insight in the pathophysiology of LRTI and provide functional and anatomic feedback on treatment effects of supporting therapies. Recently the late effect on oral microcirculation parameters was measured in IR oral mucosa when compared to healthy oral mucosa in a chairside setting using a CytoCam (CC) microscope system based
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