The influence of haemoglobin concentration on the response to radiotherapy

Abstract

Hypoxia was identified many years ago as a crucial cause of radioresistance in tumours and an association between haemoglobin concentration and radiation response has been established, especially in patients with squamous cell carcinoma. The explanation for this is linked with the amount of oxygen available to the tumour tissue. A few small studies have shown that blood transfusion given to patients with low haemoglobin values (but not anaemic) prior to radiation treatment significantly increased the tumour control probability. Experimental studies in rodents have demonstrated that shifting the oxyhaemoglobin dissociation curve to the right (e.g. by increasing the 2,3 DPG level) increases the radiation response in rodent tumours whereas a left shift due to increasing CO-Hb reduces the effect of radiotherapy.

A current randomized clinical trial is addressing this question by randomizing patients with low haemoglobin concentration (<8 mmol/1 for females, < 9 mmol/1 for males) to transfusion/no transfusion prior to radiotherapy. Also an attempt to characterize the haemoglobin parameters (especially p50) in these patients, who often are heavy smokers, is underway.

Key-words:

• Haemoglobin
• oxygen delivery
• p50
• radiotherapy
• squamous cell carcinoma