Clinical Benefit of Baseline Imaging in Merkel Cell Carcinoma: Analysis of 584 Patients

Abstract

BACKGROUND: Merkel cell carcinoma (MCC) guidelines derive from melanoma and do not recommend baseline cross-sectional imaging for most patients. However, MCC is more likely to have metastasized at diagnosis than melanoma.

OBJECTIVE: To determine how often baseline imaging identifies clinically occult MCC in newly diagnosed patients with and without palpable nodal involvement.

METHODS: Analysis of 584 MCC patients with a cutaneous primary, baseline imaging, no evident distant metastases, and sufficient staging data.

RESULTS: Among 492 patients with clinically uninvolved regional nodes, 13.2% were upstaged by imaging (8.9% in regional nodes, 4.3% in distant sites). Among 92 patients with clinically involved regional nodes, 10.8% were upstaged to distant metastatic disease. Large (>4cm) and small (<1cm) primary tumors were both frequently upstaged (29.4% and 7.8%, respectively). PET-CT upstaged patients more often (16.8% of 352), than CT alone (6.9% of 231; p=0.0006). LIMITATIONS: This was a retrospective study. CONCLUSIONS: In clinically node-negative patients, baseline imaging revealed occult metastatic MCC at a higher rate than reported for melanoma (13.2% vs. <1%). Although imaging is already recommended for clinically node-positive MCC patients, these data suggest that baseline imaging is also indicated for clinically node-negative patients because upstaging is frequent and markedly alters management and prognosis.