Changes in head and neck tumor hypoxic fraction during split-course radiochemotherapy

This study explored patterns of oxygen distribution in human tumors during primary radiochemotherapy. Patients with positive nodes from head and neck squamous cell carcinoma (n = 15) were investigated before therapy, before and after a 2-week respite, and at the end of the treatment. Intratumoral tissue oxygen tension (pO2) was measured with sterile polarographic needle electrodes and a computerized histography system. The 2 lowest pO2 classes, ie, 0 and 5 mm Hg, were designated the hypoxic fraction, and the mean and median pO2 were evaluated for each tumor. In the beginning, a marked variability in tissue pO2 was found. The initial size of the hypoxic fraction ranged from 0% to 61% of measured values. At the end of treatment, 4 tumors showed an increase in mean pO2, and 7 tumors a lower mean pO2 in comparison to the initial values. However, an impressive finding was that the hypoxic fraction of 9 tumors became smaller during the pause, 1 tumor showed no change, and 1 showed an increase in hypoxic fraction. The results show that there is a widely distributed tissue oxygenation with marked hypoxic zones in human neck nodes. During radiochemotherapy, tissue oxygenation changed, with great intertumor variability. A tendency toward a decrease of the hypoxic fraction after the respite could be seen. This change in tumor oxygenation during therapy needs further evaluation.