The role of 18 F-FDG PET/CT in the management of Merkel cell carcinoma: The experience of 51 studies in our institution

Merkelcell.org Summary

Another study (this one from Spain) documenting the striking utility of PET/CT scanning in MCC, particularly at baseline, when we strongly advocate for this technology. Staging and management were altered in a large proportion of patients.

Abstract

Objectives: Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine tumor with limited evidence on the role of 18F-FDG PET/CT. The aim of this study was to assess the impact of the 18F-FDG PET/CT in the management of MCC.

Methods: Fifty-one studies of 18F-FDG PET/CT of 35 patients (19 men [54.30%]; 72.17±14.63years) with histologic diagnosis of MCC were retrospectively evaluated. The change in tumor staging and the impact on the treatment were analyzed.

Results: There were 23 PET/CT positive studies (45.10%) and 28 (54.90%) negative. Thirty four (66.7%) studies were performed for assessment of stage at initial presentation and 17 (33.3%) were performed during the follow up: 6 (35.29%) for suspected recurrence; 7 (41.18%) for restaging; 4 (23.53%) as a part of ongoing surveillance. On the basis of PET/CT results, there was a change in disease stage (SC) in 20 studies (39.20%) and impact in the management (MI) in 28 (54.90%): 11 (32.40%) SC and 12 (35.30%) MI in the initial staging; 5 (71.43%) SC and 7 (100%) MI in the restaging; 3 (50.00%) SC and 6 (100%) MI in suspected recurrence; 1 (25.00%) SC and 3 (75.00%) MI in the surveillance. 18F-FDG PET/CT incidentally detected one additional histologically confirmed cancer. The presence of nodal involvement in the beginning (0.0098; HR 3.82; 95%CI: 1.38-10.6), chemotherapy treatment (6e-04; HR 7.06; 95%CI: 2.30-21.60), size of primary tumor >2cm (6e-04; HR 7.06; 95%CI: 2.30-21.60) and positive resection margin (0.00069; HR 4.01; 95%CI: 1.46-11.00) were statistically significant prognostic factors for overall survival. There was a trend towards significance for worse overall survival with initial positive 18F-FDG PET/CT but the trend did not reach statistical significance.

Conclusion: 18F-FDG PET/CT altered the stage in 2 out of 5 studies and changed the treatment in more than half of the studies performed. The study confirms the important impact of 18F-FDG PET/CT on the management of MCC patients.