In a study involving 75 clinically heterogeneous patients with proven cervical cancer, the treatment approach was changed in 10 patients as a result of the new information gained from the PET/CT images, said Amnon Amit, MD, staff physician, Department of Obstetrics and Gynecology, Rambam Medical Center, Haifa, Israel.

PET imaging using intravenous administration of radiolabeled (F-18) fluodeoxyglucose (FDG) reveals malignant cells because of their heightened glucose uptake compared with normal cells. But unlike CT, PET imaging does not provide anatomical landmarks, Dr. Amit said. By performing both studies at the same time, clinicians can create images with the PET findings superimposed on the CT scan, thereby providing the anatomical data that is lacking in the PET images.

In this study the researchers divided 75 patients with proven cervical cancer into 3 groups. The 16 patients in Group I had been referred for radical abdominal hysterectomy; the 31 patients in Group II were imaged prior to pelvic radiotherapy; and the 28 patients in Group III were suspected of having recurrent disease. The clinicians performed whole body PET and CT, using a single hybrid imaging device, 1 hour after injecting 10 to 15 mCi of FDG.

Imaging specialists first evaluated the PET and CT scans separately, and then reviewed the fused PET/CT images to determine whether they offered additional information.

The researchers were able to obtain pathohistological examinations for extra cervical lesions from 33 patients. They determined that PET/CT offered an overall sensitivity of 60% and an overall specificity of 94%. Only 17% of patients were found to be free of disease, Dr. Amit said. The PET/CT scans provided an improved diagnosis in 32 patients by providing more precise localization and definition of lesions, and clinicians changed their management plans for 10 patients because of the hybrid images.

"In our study the overall sensitivity was only 60%. We are concerned about the low sensitivity in our data," Dr. Amit said. He noted, however, that in patients with advanced disease, the sensitivity was 87% and the specificity was 100%.

The researchers found that PET/CT reduced the number of unnecessary surgical interventions and helped modify radiation fields. They found that detection of advanced disease with PET/CT correlates with a poor prognosis, and that hybrid imaging is less accurate in detecting microscopic disease and lesions that are smaller than 1.5 cm.

"Our take-home message is that for patients with early disease, a positive scan is highly predictive of nodal metastases. But when the PET/CT is negative, a careful examination of the lymph nodes is required during surgery to rule out nodal metastases," Dr. Amit concluded.


[Presentation title: The Role of Hybrid PET/CT in the Evaluation of Patients with Recurrent Ovarian Cancer Who Are Candidates for Second Debulking. Abstract 159]

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