Metabolic assessment of Merkel cell carcinoma: The role of ¹⁸F-FDG PET/CT

Objectives Merkel cell carcinoma (MCC) is a rare aggressive skin tumor associated with a high mortality rate. The present study evaluated the role of fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) PET/computed tomography (CT) in subsequent management of patients with MCC. Methods A total of 101 consecutive ¹⁸F-FDG PET/CT studies of 46 patients with MCC (28 men, 68±15.4 years) were retrospectively evaluated and the role in clinical care was documented. Results There were 40 positive studies (40%) in 28 patients (61%); of these, 33 studies (33%) in 27 patients (59%) showed metastatic disease. Fifty-two PET/CT studies (51%) in 23/46 (50%) patients were negative. Fifty-three studies (52%) were performed for staging or restaging in 41 patients, 29 scans (29%) were performed for routine follow-up in 10 patients, nine studies were carried out for suspected recurrent disease in eight patients, and 10 studies were carried out for assessment of response to therapy in seven patients. On the basis of PET/CT results, there was a change in disease stage in 12 studies in 12 patients (26%) and further change in the management of seven patients (15%). Overall, 2/29 routine follow-up studies were positive with further impact on management in one patient. Conclusion ¹⁸F-FDG PET-CT altered the stage of one of four patients and changed the management of one of seven MCC patients. In the majority of patients, a negative ¹⁸F-FDG PET-CT study excluded active MCC with a high degree of confidence. PET-CT contributed toward patient management when performed for staging and restaging, monitoring response to treatment, and suspected recurrent disease, but not in the routine follow-up of asymptomatic patients with MCC.