The oxygen effect has particular importance in external beam radiation therapy where the killing of tumour cells with photon and electron beams in well oxygenated regions can be up to three times greater than in a poorly vasculated portion of the tumour.
Besides tumour hypoxia, the oxygen effect is also relevant to hypoxia conditions present in the normal physiology of stem cell niches such as the endosteum adjacent to bone in bone marrow and the epithelium layer of the intestine. In addition, there are non-malignant diseases where oxygenated tissues can become hypoxic such as in stenosed coronary arteries associated with cardiovascular disease.