Hypoxic (low oxygen) cells have long been known to exist in animal tumors. It is also known that hypoxic cells are more difficult to eliminate with radiotherapy than tumor cells at normal levels of oxygen (normoxic cells). However, the extent to which hypoxic cells limit the curability of human tumors is uncertain. To determine if hypoxic cells exist in human tumors and how hypoxic cells might influence the efficacy of radiotherapy, this study involves direct measurements of oxygen levels in human tumors compared to the tumor uptake of the experimental drug, 18F-fluoromisonidazole (18F-FMISO), visualized with PET scanning. 18F-fluoromisonidazole has been used with PET imaging to tell the difference between growing tumors which have high and low oxygen content.
Before beginning radiotherapy, a PET scan (series of pictures, 20 min. scan) will be performed at 2 hours after an intravenous injection of a small amount of radioactive traces drug, 18F-fluoromisonidazole (18F-FMISO) to observe the active hypoxia tumors areas. Upon completion of the 18F-FMISO PET scan, direct oxygen measurements will be obtained by placing a small needle into the tumor under computer tomographic (CT) guidance. The PET scan and needle measurements will be repeated every 4 weeks into the course of radiotherapy and again after the completion of radiotherapy. The measurement obtained by 18F-FMISO PET scanning (non-invasive technique) and by direct needle measurements (invasive technique) will be correlated with the eventual treatment outcome for future use.
