Hyperbaric oxygen in cancer

It is a well known fact that hypoxia is a common feature of different solid tumors. Local impairment of the circulatory system entails the generation of a heterogeneous population of tumor cells that are not normally supplied with oxygen and nutrients in most regions of the tumor, except those that are in close proximity to the blood vessels. The reduced cell division seen in areas with low oxygenation in tumors results in resistance to both radiotherapy and chemotherapy.

Poorly vascularized areas of the tumor may be perfused, through sub-lethal levels, by cytotoxic agents, thus generating an acquired resistance to chemotherapy. A study published in Nature magazine has also shown that hypoxia may be responsible for a variety of growth modulation effects that could generate an advantage of cancer cell growth.

Yang and his research team found that the hypoxia-induced expression of factor-1 (HIF-1), suggested to be an endogenous marker of tumor hypoxia, significantly affected the overall survival and the disease-free survival of osteosarcoma patients.

Antitumor effect of hyperbaric oxygen therapy

HBOT dramatically increases the amount of oxygen dissolved in the plasma, oxygenates the hypoxic tissues and promotes neovascularization, eventually leading to increased blood flow. These features of hyperbaric oxygen therapy increase the partial pressure of oxygen inside the tumor and make it more susceptible to radiotherapy.

HBOT has been extensively and successfully used in radiotherapy to increase radiation sensitivity and tumor oxygenation. In the same way, hyperbaric oxygen therapy enhances the perfusion of chemotherapeutic agents into hypoxic tumors and the susceptibility of tumor cells to such drugs.
Several studies have suggested that hyperbaric oxygen therapy can promote the growth or recurrence of malignancy by promoting angiogenesis, while other studies have shown inhibitory effects on tumor growth. However, two independent research groups have recently reviewed experimental and clinical data from the literature of the past 50 years and concluded that intermittent exposure to HBOT had no stimulatory effects on primary or metastatic cancer growth.
Currently, HBOT is used clinically in combination with radiotherapy and chemotherapy as a treatment approach of malignant tumors.