Localised disease in cancer of unknown primary (CUP): The value of positron emission tomography (PET) for individual therapeutic management

Background: Two to four percent of cancer patients present with CUP syndrome. Median survival for localised disease is 20 and for disseminated disease, seven months. For localised disease, curative treatment is more likely and individual therapeutic strategies become more important. After conservative diagnostic procedures including MRI, the primary is detected in less than 25%. The diagnostic value of PET and its influence on therapeutic strategies was evaluated. Patients and methods: Forty-two patients with localised CUP were investigated from 5 of 98 to 10 of 2000. The presenting site was lymph node metastasis in 34 and visceral metastasis in 8 patients. After a median of 7 (3-11) diagnostic procedures without detection of the primary, but evidence of localised disease, PET was performed with fluorine-18-fluorodeoxyglucose. Results: In 26 of 42 patients (62%), a primary was suggested by PET and confirmed in 18 (43%). In 5 of 18 patients beyond localised disease, additional dissemination, not detected by previous diagnostic measures, was diagnosed by PET. Overall, dissemination was only detected only by PET in 16 of 42 patients (38%). In 29 of 42 patients (69%), the PET result influenced selection of the definitive treatment. Conclusion: In CUP patients, PET has a certain impact on detection of the primary as well as of the disseminated disease, and may also have a certain impact on therapeutic management.