Planar coincidence scintigraphy and PET in staging malignant melanoma

This study describes a comparison of simulated planar positron coincidence scintigraphy (PCS) with PET in the whole-body staging of patients with malignant melanoma using 2-18F-fluoro-2-deoxy-D-glucose (FDG).

In 55 patients with either known metastatic or newly diagnosed malignant melanoma, whole-body PET scanning was performed on a conventional full-ring dedicated PET tomograph, and multiaxial sections were obtained. Furthermore, anteroposterior projection images simulating images of a dual-head Anger camera operating in coincidence mode were obtained from the PET raw data. Each study was evaluated separately and blindly. Imaging findings were confirmed by biopsy or by at least one imaging modality in addition to PET.

A total of 108 lesions were evaluated, of which 76 proved to be melanoma metastases. Whole-body PET correctly demonstrated 68 metastases, 6 lesions were classified as questionable metastases and 2 were missed. Whole-body PCS correctly demonstrated 14 metastases, 22 lesions were classified as questionable metastases and 40 metastases were missed. The sensitivities of whole-body PET and whole-body PCS were 89% and 18%, respectively. In PCS lesions in regions of high background activity, such as in the abdomen, were missed more often than in PET (p < 0.05). The tumor-to-background contrast was generally lower in PCS than in PET. A further decrease in PCS detection was found in lesions of < 22 mm in diameter.

The lack of sensitivity precludes the clinical use of whole-body PCS in staging malignant melanoma.