PET May Be Used to Detect Recurrences Of Ovarian Cancer

BALTIMORE--Some 60% to 80% of ovarian cancer patients recur afterthe first round of treatment, and "only about 15% of ovariancancer patients who test positive at second-look laparotomy surviveas long as 5 years," Karl F. Hubner, MD, of the Universityof Tennessee, Knoxville, said at a nuclear oncology conferencesponsored by the Johns Hopkins Medical Institutions.

Unless the patient undergoes second-look laparotomy, finding arecurrence is chancy, Neal B. Rosenshein, MD, of Johns HopkinsSchool of Medicine, said in his presentation.

A CT scan, Dr. Rosenshein said, is about as good as a "flipof a coin," and scintigraphy has about the same value. Usinga CA 125 assay is 100% accurate if positive, but no better thanCT if negative. Laparoscopy, besides being painful and expensive,has a false-negative rate of 35%.

In a search for better noninvasive tools, Dr. Hubner has beenstudying positron emission tomography (PET) using F-18 fluorodeoxyglucose(FDG). Regional and whole body scans have proved useful in locatingmetastatic spread, Dr. Hubner said. Studies show that standardFDG uptake values above 3.2 strongly predict cancer.

"Taken together, negative PET and CT scans are sufficientlyspecific that they may obviate second-look surgery," he said."This combination has the highest accuracy for both diagnosisand exclusion of ovarian cancer." He also noted that PETimaging can be used to optimize the timing of second-look surgery.

Furthermore, PET , a noninvasive procedure, is less expensive:$2,200 at Dr. Hubner's Knoxville center versus $15,000 for second-looksurgery (for a 5-day hospital stay without complications).

Drawbacks to the process include GI tract activity, which canbe minimized by looking at that activity over time, he said. PETscan may be obscured by postoperative abscesses or infectionsand, in any case, cannot detect lesions under 7 mm in diameter.Dr. Hubner suggests irrigating the bladder during the scan tokeep bladder activity low.

But the problem remains what to do after detecting a recurrence.Surgery confers no further survival advantage, Dr. Rosensheinsaid. Having used chemotherapy the first time, there is littleto give the patient the second time around. "It's a frustratingissue. We need less invasive diagnostic tools, but the issue isn'tdiagnostic modalities but rather the need for new therapeuticapproaches," he said.