Solid tumours often have highly disorganised vasculature that results in low oxygenation.
This combined with high metabolic rates leads to oxygen demand outstripping supply causing
tumour hypoxia. Hypoxia drives multiple cellular processes involved in the hallmarks of
cancer. Tumour hypoxia also decreases the effectiveness of anticancer treatments. This is
especially true for patients treated with radiotherapy since it has been long recognised that
hypoxic tumour cells require 3 times the dose of radiation to cause the same amount of cell
death as cells irradiated under normal oxygen conditions.
To date, the majority of attempts at overcoming tumour hypoxia have focused on increasing
oxygen supply. However, such techniques have produced modest benefits at best and
subsequently have not been adopted into current clinical practice.
An interesting alternative approach to tackling tumour hypoxia is to decrease oxygen 'demand'
by reducing tumour oxygen consumption. This strategy has been suggested to be more effective
in reducing hypoxia than previous methods aimed at increasing oxygen delivery.
Pre-clinical data demonstrates that the commonly prescribed anti-protozoal drug atovaquone
significantly reduces oxygen consumption in a variety of tumour cell lines in vitro. This
reduction in oxygen consumption leads to a profound reduction in tumour hypoxia in animal
models. It is anticipated that if these effects on tumour hypoxia could be reproduced in
humans, that their tumours could be rendered markedly more sensitive to radiotherapy.
This window of opportunity trial will assess whether atovaquone significantly reduces tumour
hypoxia in adult patients referred for surgery with suspected non-small cell lung cancer.
This will be assessed using a combination of functional imaging and circulating markers of
hypoxia. If atovaquone is demonstrated to result in a reduction in tumour hypoxia, larger
clinical trials will be conducted to determine whether this well-tolerated and inexpensive
agent improves radiotherapy efficacy and clinical outcomes.