The link between oxygen and tumour cells has been established, not only in that low oxygen levels can result in cancerous cells but that also by increasing oxygen these tumour cells can be destroyed. Finding a way to do this has been difficult as blood vessels supplies to tumour sites become reduced and so getting oxygen to the site is proving difficult.
Not only are tumour cells able to survive in low oxygen environments but these oxygen-starved cells are more difficult to kill with radiation treatment than normal healthy tissue. Scientists wanted to develop a way in which oxygen could be infused into the tumour, not only to create a more oxygen rich environment to help slow down growth but also so that they can be nuked by treatment more effectively.
One such idea has been to inject tiny oxygen-filled bubbles into a patient’s bloodstream. Microbubbles are miniature gas bubbles, containing oxygen or air, which can be suspended in a liquid such as blood. Due to their size, they can pass through even the smallest of blood vessels, and are commonly used together with medical ultrasound imaging. Microbubbles reflect ultrasound better than blood or soft tissues, which allow them to be used for highlighting blood in ultrasound images.
These microbubbles would travel to the tumour site via the bloodstream, and as the tumour’s blood vessel walls are leakier due to the effects of the tumour, they would gain access to the tumour more easily. These bubbles would then be burst to release oxygen within the tumour.
The ultrasound community already use a similar idea of using gas-filled microbubbles to improve the contrast of images. High-intensity localised ultrasound could be used to view and then rupture these bubbles at the specific site that you want.
In a recent experiment with mice it was shown that the ones treated with oxygen-containing microbubbles released their oxygen and resulted in a detectable oxygen level increase of 30 mmHg at the tumour site. Even a 10-15 mmHg increase would make the tumours twice as sensitive to radiation. Testing is now going ahead to prove whether the radiation does indeed become more effective in killing the tumour cells.
If this idea becomes a reality then cancer sufferers will require less chemotherapy and radiation therapy and experience less side effects as well as having an increased chance of destroying the tumour.
In the meantime we only have conventional methods of increasing oxygen at our disposal, such as oxygen therapy which can increase oxygen levels within the bloodstream, although only a small amount can pass through into the tumour site. Prevention is also being looked into, as low-oxygen levels are a main cause of cancerous cells there are thoughts about putting high risk patients onto low level oxygen therapy regimes as a preventative measure to try to reduce the risk of tumour sites developing.