Importance of hemoglobin concentration and its modification for the outcome of head and neck cancer patients treated with radiotherapy.

INTRODUCTION: Hypoxia induced radioresistance has been acknowledged for decades. One of the indirect evidences of the influence of hypoxia on radiation response comes from the observations of a correlation between tumor control and hemoglobin level. This review examines the clinical data on the prognostic and predictive role of hemoglobin level and hemoglobin manipulation in radiotherapy of squamous cell carcinomas of the head and neck, a tumor type where hypoxic radioresistance have been previously documented. THE INFLUENCE OF HEMOGLOBIN CONCENTRATION ON TUMOR OXYGENATION AND OUTCOME: The aim is to evaluate the existing literature for information of the influence of hemoglobin concentration and hemoglobin modifications on tumor oxygenation and outcome in head and neck squamous cell cancer patients. The data from several randomized trials show that while most studies have confirmed the prognostic value of hemoglobin, increasing the hemoglobin level through transfusion or erythropoietin stimulation did not result in improved outcome for patients with low initial hemoglobin levels. Clinical studies showed that smoking reduced the oxygen carrying capacity of the blood through formation of carboxyhemoglobin, and lead to poorer response to radiotherapy in smokers compared to non-smokers. Smoking also increased the risk of the development of secondary cancers. CONCLUSION AND FUTURE PERSPECTIVES: In conclusion, low hemoglobin is a significant negative prognostic factor for radiotherapy of head and neck cancer. Correction of pre-treatment low hemoglobin by blood transfusion and/or erythropoietin stimulating agents does, however, not improve the outcome. Smoking leads to a decrease in effective hemoglobin and poorer treatment outcome. Smoking should be avoided in order to improve the therapeutic efficacy of radiotherapy and development of other smoking-related diseases and/or secondary cancers.