Purpose: Investigating tumor oxygenation in breast cancer with the Eppendorf device is hampered by the deep location and inadequate fixation of the tumor within the breast. In order to ensure the correct site of pO(2) measurements, guiding aids were introduced and the reliability of the refined method was evaluated.
Material and methods: For guidance of the needle electrode, a metal trocar was inserted up to the tumor rim. Its positioning and all transtumoral tracks of the needle electrode were monitored continuously by ultrasonography. Thus, 150 tumor measurements in 148 patients were evaluated. In a phantom, the possible influence of the metal trocar was assessed and the measurements of two histographs with five different needle electrodes were compared.
Results: In 88% of measurements (132/150) complete or partial sonographic demarcation of the tumor was possible. 83.2% of the tracks (437/525) could be controlled by ultrasonography. Overall, in 60% of measurements (90/150) all values derived reliably from within the tumor. In vitro, an influence of the metal trocar on the measurements could be excluded. Differences between histographs were in accordance with tolerance limits.
Conclusion: From theoretical considerations and the phantom experiments a significant negative impact of the technical modifications could be excluded. Instead, the method described here showed to be beneficial in measuring tumor oxygenation in breast tumors. The authors strongly advise to consider exclusively intratumoral pO(2) values as proven by ultrasonography for oxygenation profiling, as in 40% of all measurements the origin of single pO(2) values or tracks was questionable.