18F-DCFPyL PET/CT in High-grade Epithelial Ovarian Cancer (PET HOC)

In patients with ovarian cancer, identifying the volume and exact locations of disease is of paramount importance prior to deciding on upfront surgery versus chemotherapy. Currently, most clinicians use CT scans to determine the extent of disease; however, this tool has limited sensitivity and specificity. 18F-Fluorodeoxyglucose (=FDG) PET scans have been previously assessed with only limited success; therefore, FDG PET scans have not been universally incorporated into the workup of patients with ovarian cancer. A further noninvasive tool that would accurately map disease extent is needed to better select therapy for ovarian cancer patients, reduce the rate of aborted surgery and associated complications, and hopefully improve overall outcome. "Glutamate carboxypeptidase II (GCP-II)" is a type of an enzyme on the surface of cells. It has additional names including prostate specific membrane antigen (PSMA). It is expressed by normal tissues such as salivary glands, as well as by multiple malignant tumors, often in the abnormal blood vessels of these tumors. A recent study has examined the expression of this enzyme in gynecologic cancers including primary and metastatic ovarian cancer. The authors showed a high expression of this enzyme at special staining performed on surgical tumor samples. In other cancers, such as prostate cancer PET with GCP-II (=PSMA PET) has shown very high sensitivity and high specificity for the detection of tumor sites, even when CT is negative. In this study the investigators will be assessing the performance of this special PET scan using a PSMA tracer called "18F-DCFPyL". The investigators will investigate the ability of 18F-DCFPyL PET scans to detect sites of disease in patients with ovarian cancer. Disease sites seen on PET will be compared to what is seen on the standard CT scan, and to what is found at time of surgery (if surgery is performed). The rationale for this study is that there is a need for better noninvasive tools that will map disease extent in HG EOC. A recent study has shown that at immunohistochemistry GCP=II is overexpressed in ovarian cancer tumors, both primary and metastatic. GCP-II (=PSMA) has been used clinically to assess patients with prostate cancer and many other tumours have been shown to be PSMA-avid on PET (including renal cell carcinomas). The purpose of this study is to determine whether HG SOC are 18F-DCFPyL (=GCP-II)-avid and to compare the performance of this PET to CT and findings at time of surgery. Primary Objective To determine whether HG EOCs are 18F-DCFPyL avid on PET/CT. Secondary Objectives: To compare the sites of disease identified on PET/CT to contrast-enhanced CT (standard of care). To determine whether there is heterogeneity in 18F-DCFPyL-avidity at different tumor sites.