Anecdotal studies have reported explosive tumor growth in patients with a history of squamous cell carcinoma after hyperbaric oxygen (HBO) treatment. Conflicting experimental results have followed. In this study, squamous cancer cells were subjected to daily HBO treatment. No difference in cellular proliferation was noted in vitro when comparing HBO and control treated cells (P = 0.534). Similarly, immunostaining for in vivo DNA synthesis failed to demonstrate any significant difference in the number of proliferating cells after treatment with HBO (P = 0.388). No significant difference in tumor volume or mass was found after in vivo implantation (P = 0.471). HBO was found to reduce tumor hypoxia, which trended towards significance when compared with controls (P = 0.057); however, there was no difference in serum VEGF levels or vessel ingrowth. Thus, even though HBO may reduce the levels of hypoxia within squamous cell tumors, it does not appear to enhance short-term growth or promote cellular proliferation or angiogenesis.

Schönmeyr, Wong, Reid, Gewalli, Mehrara, , , , (2008). The effect of hyperbaric oxygen treatment on squamous cell cancer growth and tumor hypoxia. Annals of plastic surgery, 2008 Jan;60(1):81-8. https://www.ncbi.nlm.nih.gov/pubmed/18281803