MAY 31, 2012
This retrospective case series in the April issue of the American Journal of Ophthalmology investigated the value of whole-body positron emission tomography/computed tomography (PET/CT) as a screening tool for patients with uveal metastasis. The results suggest that this technology can be useful for the clinical evaluation of these patients, allowing for the screening of the entire body, directed extraocular biopsy and detection of the primary cancer.
The study included 18 patients with uveal metastatic tumors. They underwent whole-body 18-fluoro-2-deoxyglucose (18F FDG) PET/CT as a screening tool for cancer staging, and to evaluate the intraocular tumor and for multiorgan metastatic disease. They all had either no history of malignancy (n=11) or a past medical history of malignancy without known active metastasis or known systemic cancer (n=7).
PET/CT detected the occult primary nonocular malignancy in each of the 11 patients without a history of cancer and confirmed disease progression in the seven patients without a history of metastasis. The imaging revealed multiorgan metastasis in all patients. Discovery of nonocular metastatic sites allowed for tissue biopsy and the confirmation of primary tumor pathology in 67 percent of cases. PET/CT demonstrated that lymph nodes and bone were the most common metastatic sites.
The intraocular tumor was detected in five of the cases. Uveal biopsies were deferred in all of these patients.
The authors say that PET/CT is particularly useful in detecting bony metastasis, which was present in 10 patients and can be difficult to detect on CT alone and indistinguishable from benign lesions. Four of the osseous lesions detected later served as the source for tissue biopsy.
The study's findings suggest that PET/CT is a valuable diagnostic modality in patients who present with suspected uveal metastasis in the absence of known primary or known metastatic disease. The authors conclude that whole-body PET/CT allows for the detection of more extensive disease than would be evident on routine segmental radiographic imaging modalities. They say that the detection of multifocal metastatic disease can allow for more appropriate, more targeted therapeutic management.
A larger prospective study would be needed to determine to compare the efficacy of whole-body PET/CT with other imaging modalities. Until such data become available, the authors say the current study suggests that PET/CT can be used to locate a primary malignancy, evaluate the intraocular tumor and detect multiorgan metastasis.