Effect of hypoxia on the survival of tumour and endothelial cells subjected to ionising radiation

Radiotherapy is a highly effective treatment for various types of malignant tumors, both in early and late stages of the disease. Because of its cost-benefit ratio, approximately half of all patients diagnosed with cancer are treated with radiotherapy. However, radiotherapy often fails to
eradicate all cells within the tumor; the tangible manifestation of this failure is a local, regional or systemic recurrence of the disease1 . Although great therapeutic and experimental advances have occurred over the last decade, much of the biological and chemical underpinnings of this technique remain to be explored2. Several elements are essential to understanding the success or failure of the treatment. Among the most important of these are the differential repair of tumor and normal cells between fractionated treatments, the redistribution of tumor cells between fractionated
between fractionated treatments, the redistribution of cells in radiosensitive phases of the cell cycle, the repopulation of tumor cells between fractionations, the oxygenation conditions of the tumor cells before and during treatment, the intrinsic radiosensitivity of each type of tumor, and the type and energy of ionizing radiation used in the treatment3 . On the other hand, endothelial cells have recently been implicated as critical determinants of radiation response in healthy and tumor tissues.