HETEROGENEITY OF POLAROGRAPHIC OXYGEN-TENSION MEASUREMENTS IN CERVIX CANCER - AN EVALUATION OF WITHIN AND BETWEEN TUMOR VARIABILITY, PROBE POSITION, AND TRACK DEPTH

Purpose: To evaluate the heterogeneity of cervix cancer oxygenation as measured using the Eppendorf polarographic electrode and define the o ptimal number of measurements required to adequately sample a cenix ca ncer. Methods and Materials: Two to 6 tracks with 20-30 measurements p er track were obtained in each of the 44 patients evaluated, One hundr ed sixty-eight tracks and 4719 measurements formed the basis of this a nalysis, Median pO(2) and hypoxic proportion (HP5), defined as the per centage of pO(2) values <5 mmHg, were calculated for each track and fo r each tumor, Within-tumor (W) and between-tumor (B) variability in ox ygenation was evaluated using a variance component analysis, The stand ard error of the measured HP5 with each additional track in each patie nt was analysed as a function of the total number of tracks. Results: The ratio W/W + B was 0.67 and 0.76 for median pO(2) and HP5, respecti vely, indicating that multiple measurements are needed to adequately s ample a tumor, The median value of the standard error of the HP5 decre ased from 7.0 to 4.0% from the first to the fifth track, respectively, It was estimated that adding the sixth track would only result in a s mall change (<0.3%) in the standard error. There was no significant di fference in oxygen tension measurements as a function of the location of the measurements around the circumference of the cervix or the dept h along the measurement tracks. Conclusions: There is significant with in tumor variability in oxygen tension in cervix cancer, Five tracks w ith 20-30 measurements per track is optimal to sample the oxygenation status of a cervix cancer, The present data does not suggest that ther e is a significant difference related to the position in the tumor at which the pO(2) measurements were taken. (C) 1997 Elsevier Science Inc .