PET imaging in ovarian cancer

The FDG uptake within the ovary in a postmenopausal woman is pathologic and is suggestive of cancer diagnosis. Combined PET/CT provides anatomic and metabolic information and has shown to be an important imaging modality in N and M staging of ovarian cancer but its role is limited in T staging. PET/CT can detect nodal and distant metastasis with high sensitivity and accuracy. This information is crucial for treatment and surgical planning and noninvasively selecting surgical candidates and patients who will benefit from upfront chemotherapy. Also, PET/CT demonstrated great value in evaluation of treatment response and predicting prognosis in ovarian cancer. Additionally, PET/CT can detect recurrent disease particularly in patients with rising CA-125 levels and negative imaging results. However, there are false positive and false negative results associated with PET which radiologists need to be aware of when interpreting PET images. False positive results have been reported in patients post treatment, with infectious/inflammatory processes, endometriosis, benign cystic lesions and physiologic ovarian uptake in premenopausal women. Also, Physiologic uptake of gastrointestinal tract can be mistaken for serosal implants. False negative results have been reported in small lesions (<5mm), cystic, necrotic and mucinous tumors as well as low grade and borderline tumors. Recently integrated PET/MRI has shown superior results in characterization of ovarian masses due to higher soft tissue contrast provided by MRI without any ionizing radiation exposure to the patient. Also, bowl involvement by carcinomatosis is better delineated by PET/MRI which can help in selecting nonsurgical cases and avoiding unnecessary laparotomies.