Imaging Tumor Hypoxia With 18F-EF5 PET in Recurrent or Metastatic Clear Cell Ovarian Cancer

This study involves one visit to the BCCA - Vancouver Centre to undergo one EF5-PET/CT scan. The visit will take about 4 hours to complete and no follow-up visits are required. * Participants will fill out a short medical questionnaire asking routine information (treatment history, previous surgeries, medications, allergies, etc.) that will take about 5-10 minutes to complete. * Next they will be weighed and vital signs measured (blood pressure, heart rate and blood oxygen saturation). * An IV is inserted into a vein in the participant's arm. At the same, a small amount of blood will be taken to measure their blood glucose level. * The participant will receive an IV dose of 18F-EF5. * Five minutes after the injection, blood pressure and heart rate will be checked again. * Participants will then be free to leave the functional imaging department for a period of 180 minutes while the 18F-EF5 circulates throughout their body. Participants are free to eat as normal during this period. * Participants will undergo the 18F-EF5 PET scan, which will take about 20 minutes. The participant will need to lie still on the scanner bed during the entire scan. * The 18F-EF5 PET scan will be reviewed by a BC Cancer Agency doctor specialized in PET and the results will be sent to their referring doctor. Optional Biopsy Procedure: Participants will have the opportunity of participating in an optional biopsy procedure for the purposes of further studying contemporaneous tumour tissue (contemporaneous with the EF5-PET) for markers of hypoxia, apoptosis, angiogenesis etc. The tissue will also be compared to archival material, and this will allow researchers to study the evolving changes in tumours following treatment. Patients who consent to undergo a biopsy will be booked to the Diagnostic Imaging Department at the Vancouver Centre. Ultrasound guidance will be used to obtain up to 5 core biopsies from an accessible lesion(s). Up to 2 distinct tumour areas may be sampled. The standard procedure required for a core biopsy will be followed, which will include pre-biopsy lab tests, sterile technique, and when needed, post biopsy observation. The core biopsies will be formalin fixed and paraffin embedded (FFPE). A BCCA pathologist will review representative slides of each paraffin block to ensure the presence of tumour tissue. The FFPE block will then be sent to the laboratory for immunohistochemistry staining and further interpretation.