Direct oxygen partial pressure (pO2) readings in cancers of the cervix and in the normal cervix of nulliparous or parous women were obtained using a computerized pO2 histography system. The oxygenation status of the tumors was evaluated as a function of clinical staging and histological grading. pO2 measurements were performed with a customized electrode system in conscious pre- and postmenopausal, untreated patients with well-defined arterial blood gas status.
With this technique, pO2 measurements in the normal cervix of nulliparous women resulted in oxygenation patterns which were characteristic for normal, adequately supplied tissues (median pO2, 48 mm Hg) with approximately 1% of the pO2 values grouped between zero and 2.5 mm Hg, i.e., in a range with less than half-maximum radiosensitivity. As a rule, the mean (and median) pO2 values were distinctly lower in the normal cervix of parous women (most probably due to scar formation following vaginal delivery) and in malignancies. In the normal cervix of parous women the median pO2 value was 13 mm Hg (with approximately 14% of the pO2 readings in the lowest class), 14 mm Hg in International Federation of Gynecologists and Obstetricians I/II tumors (2% of the readings in the lowest pO2 class), and 11 mm Hg in International Federation of Gynecologists and Obstetricians III/IV cancers (1% of the pO2 data in the lowest class). To date, 5 of 18 cervical cancers exhibited pO2 values between zero and 2.5 mm Hg. The oxygenation pattern in cervical cancers and the occurrence of hypoxia and/or anoxia did not correlate with either the clinical stages and histological grades or with a series of clinically relevant parameters (e.g., tumor size). No significant differences were found between pre- and postmenopausal tumors, between squamous cell carcinomas and adenocarcinomas, and between endophytic or exophytic tumors.
From these studies there is clear indication that the oxygenation status of individual tumors cannot be predicted on the basis of staging and/or grading, predominantly because of the pronounced tumor-to-tumor variabilities. Evaluation of the tissue oxygenation of individual tumors is thus mandatory to prove that tumor oxygenation can predict the overall prognosis and/or treatment outcome.