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

Neha Singh, BS, Nora A. Alexander, BS, Kristina Lachance, MS, Christopher W. Lewis, MD, Aubriana McEvoy, MD, Gensuke Akaike, MD, David Byrd, MD, Sanaz Behnia, MD, Shailender Bhatia, MD, Kelly G. Paulson, MD, PhD, Paul Nghiem, MD, PhD

J Am Acad Dermatol . 2020 Jul 21;S0190-9622(20)32265-9. doi: 10.1016/j.jaad.2020.07.065.

PMID: 32707254

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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.

J Am Acad Dermatol . 2020 Jul 21;S0190-9622(20)32265-9. doi: 10.1016/j.jaad.2020.07.065.