Detection of melanoma metastases with thallium-201 scintigraphy.

UNLABELLED: Thallium-201 accumulates well in various malignant tumors. The aim of this study was to evaluate the potential of 201Tl imaging in patients with metastatic melanoma.

METHODS

Fifty patients with suspected melanoma metastases were studied after intravenous injection of a mean tracer activity of 100 MBq 201Tl-chloride. We took sequence images up to 5 min (15 sec/image) and immediate whole-body images with a double-headed camera and a high-resolution collimator.

RESULTS

Of 36 patients with metastatic melanoma confirmed by histopathology, metastases were detected in 28 patients using 201Tl imaging. The tumor-to-background ratio ranged from 2.0 to 4.5 (mean 3.2). There were 8 patients with false-negative findings (sensitivity = 78%). Five false-negative findings were lymph nodes greater than 1.5 cm with tumor-to-background ratios lower than 1.5. Only a few cutaneous metastases smaller than 1 cm could be detected. There was one false-positive finding of an inflamed lymph node. The optimum time for imaging was 2-5 min postinjection.

CONCLUSION

These data suggest that 201Tl imaging is an accurate method for the detection of melanoma metastases. The short waiting period after injection, the lack of side effects and the sensitivity of about 80% may qualify this method as a routine investigation in patients with high-risk melanoma.