Tumor detection with radiopharmaceuticals.

The most common primary ocular tumor in adults is malignant melanoma of the choroid. Metastatic tumors to the choroid occur with the same frequency. The radioactive phosphorous uptake test is used most often as a nuclear diagnostic test. The test does not differentiate melanomas from metastases, and it is necessary to perform surgery for proper placement of a detection device within a distance of 1-2 mm of the tumor. These deficiencies leave ophthalmologists with a pressing need for a gamma-emitting radiopharmaceutical that would facilitate noninvasive identification of choroidal melanoma. This need is made more urgent by the fact that recently, radiation therapy has been used to treat these tumors rather than enucleation. Eyes then harbor irradiated melanoma whose status is unknown. The tumor rarely decreases in size more than 25% to 50%. There is thus a need for a specific diagnostic test to assess the nature of the tumor and the effectiveness of therapy.