Society of Nuclear Medicine 2009: Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography May Be Superior to CA-125 in Detecting Ovarian Cancer Recurrence
TORONTO, ONTARIO, June 17, 2009 — Fluorodeoxyglucose (FDG)-positron emission tomography/computed tomography (PET/CT) can provide a more precise assessment of recurrence and outcome in ovarian cancer than the standard serum tumor marker, a study presented at the Society of Nuclear Medicine 56th Annual Meeting has found.
Ovarian cancer is the fifth most common cancer in women, noted presenter Mehrbod Javadi, MD, a second-year resident in the Division of Nuclear Medicine, Department of Radiology, at The John Hopkins University in Baltimore, Maryland.
"It is a very debilitating disease for patients who have late-stage ovarian cancer, which is how it is diagnosed many times," said Dr Javadi.
"CA-125 is what has been used in the past to monitor patients. FDG-PET/CT represents a new and innovative way to look at patients and assess them for recurrent disease," he explained. "We wanted to look at the differences, look at the combined value, and compare the prognostic value of FDG-PET/CT [and] CA-125 monitoring."
Dr Javadi et al retrospectively looked at 30 patients who had been diagnosed with stage III/IV ovarian cancer with CA-125-producing tumors. Patients had 157 PET/CT scans and serial CA-125 screenings. Patients were followed for either pathologic or clinical outcome based on all available clinical data, including subsequent imaging, according to Dr Javadi.
"If someone had a negative PET scan, then a positive [magnetic resonance imaging] in 3 months, and a positive PET scan right after that, it would have been a false-negative PET scan that was initially seen," said Dr Javadi. "We wanted to be as rigorous as we could in evaluating PET/CT. Whether or not it was microscopic disease at the time, we still stated that it was a false-negative scan."
The mean follow-up time in the study was 5 years, noted Dr Javadi.
The study found PET/CT sensitivity in identifying recurrence to be 90%, better than CA-125 analysis using the Bristow (58%) or the Gynecologic Cancer Intergroup (GCIG; 26%) criteria. For specificity, PET was 91%, Bristow 89%, and GCIG 100%. The positive predictive value of PET, Bristow, and GCIG techniques were 91%, 85%, and 100%, respectively. The negative predictive value of PET, Bristow, and GCIG were 90%, 67%, and 57%, respectively.
Investigators concluded that a negative PET scan subsequent to primary treatment or successful treatment of recurrence is associated with a mean disease-free survival of approximately 1.5 years.
"Having a negative PET after primary therapy was predictive of greater progression-free survival than . . . a positive PET right after primary therapy," said Dr Javadi. "We didn't see the same difference [in progression-free survival] with CA-125 analysis."
The next step is to conduct a prospective randomized study with a set protocol and set follow-up time, added Dr Javadi.
"I do see an important role for PET technology in ovarian cancer," said Peter Conti, MD, PhD, past President of the Society of Nuclear Medicine and Professor of Radiology at the University of Southern California at Los Angeles.
"Blood markers and tests like CA-125 tell you that there is an abnormality, but they don't tell you where the abnormality is," Dr Conti told Medscape Radiology. "Moreover, not all cancers are CA-125 positive. While it is useful for screening, it is useful for screening in a select population that has the expression [of CA-125] at baseline."
The study raises the merit of developing a collection of information that combines data from blood markers, imaging, and clinical examination, according to Dr Conti. "The composite of all that information is more powerful [than using a single serum tumor marker]," said Dr Conti.
Source: Medscape Medical News
