A BOLD appraisal of cancer

Tissue hypoxia is a biological condition characterized by oxygen deficiency at the tissue level. Hypoxia has been seen to play a crucial role in tumor recurrence in head and neck cancer patients. The detection and assessment of tumor hypoxia plays a critical role in both validation and development of hypoxia modification therapies. Hypoxic cancers being more resistant to radiotherapy and chemotherapy, attempts have been made to improve the response of hypoxic cancers to radiotherapy through the use of radiosensitizers such as carbogen and others. Several techniques to assess the status of tumor oxygenation have been developed in the past, among which functional imaging techniques remain the most validated. Blood-oxygen-leveldependent magnetic resonance imaging (BOLD MRI) is a non-invasive functional imaging technique that can recognize hypoxic cancers which will respond to accelerated radiotherapeutic treatment with radiosensitizers. BOLD MRI employs a T-sensitive sequence which can detect a transient rise in signal during oxygen inhalation. This increase in signal intensity is caused by the reduced paramagnetic effect due to a decrease in the blood deoxyhaemoglobin level within cancer. Hence, BOLD MRI can detect reduced hypoxia in the malignant solid tumors and may pave the path for more conservative treatment approach for hypoxic head and neck cancers in future.