PET plus CT - best test for ovarian cancer

Jun 5 2007

An advanced molecular imaging technique influenced the management of women with ovarian cancer, detected more sites of disease and identified women whose disease was likely to progress, according to an Australian study released during the 54th Annual Meeting of SNM, the world's largest society for molecular imaging and nuclear medicine professionals.

The study shows that positron emission tomography (PET)/computed tomography (CT) imaging "is a much better test for patients with suspected recurrent ovarian cancer and is the preferred imaging technique," said Michael J Fulham, professor and clinical director of Medical Imaging at Sydney South West Area Health Service and head of the Department of PET and Nuclear Medicine at Royal Prince Alfred Hospital in Sydney, Australia.

"PET/CT, using fluorodeoxyglucose or FDG, detected many more sites of disease than were found with routine imaging both within and outside the abdomen," said Fulham in relaying the study's results. "PET/CT influenced treatment decisions in 59 percent of the 90 women and identified those whose disease was more likely to progress within 12 months," he added. "Our findings also suggest that there is an opportunity for technology replacement, replacing routine CT of the abdomen and pelvis, with PET/CT with the radiotracer FDG, thus reducing costs and providing better answers for patients and referring doctors," said Fulham.

Ovarian cancer, cancer that forms in tissues of the ovary, is the leading cause of death in women with gynecologic cancer, noted Fulham. In the United States, reports indicate that more than 22,000 new cases and more than 15,000 deaths attributed to ovarian cancer are expected this year. "Unfortunately, while positive results are possible if the disease is detected early, most women have advanced disease by the time they are first diagnosed," said Fulham.

Initial treatment is surgery followed by chemotherapy. If the cancer recurs, the treatment options include additional surgery or radiotherapy, if the disease is localized, and chemotherapy. "Patients who are able to have surgery, and the surgery removes most of the tumor, have better outcomes than those where a large amount of tumor remains after surgery or in patients who are unable to have surgery. In patients where surgery cannot be performed, there is indirect evidence that symptom-free survival can be improved if chemotherapy is initiated earlier, rather than later, when the patient is symptomatic," said Fulham. "Unfortunately, available imaging technology (such as CT and ultrasound) underestimates the extent of the disease, so women who could benefit from additional surgery are difficult to identify," he added.

"This is the largest prospective study thus far undertaken with PET/CT," said Fulham, indicating that 90 women, from three states in Australia, underwent standard tests and a PET/CT scan. Also, 34 referring doctors, including gynecologic surgeons, radiation oncologists and medical oncologists, were asked to assess the impact of the PET/CT on patient management.

"The next step in this research will be to attempt to identify those patients with residual disease after the initial diagnosis and after initial treatment has been completed, with the hope of positive outcomes for more patients by identifying those with residual active disease much earlier on," said Fulham.

PET is a powerful medical imaging procedure that noninvasively demonstrates the function of organs and other tissues. When PET is used to image cancer, a radiopharmaceutical (such as FDG, which includes both a sugar and a radionuclide) is injected into a patient. Cancer cells metabolize sugar at higher rates than normal cells, and the radiopharmaceutical is drawn in higher concentrations to cancerous areas. PET scans show where FDG is by measuring the high-energy photons emitted by the drug and produce three-dimensional images of those substances functioning within the body. PET scanning provides information about the body's chemistry, metabolic activity and body function, while CT supplies anatomic images.