Unmasking hidden Merkel cell carcinoma recurrences: Three illustrative cases of patients with rising viral oncoprotein antibody levels and challenge of requiring multi-modal imaging to detect clinical disease

Abstract

Merkel cell carcinoma (MCC) is a neuroendocrine skin cancer with a high risk of recurrence and metastasis. Regular surveillance through physical exams and imaging studies is crucial for the timely detection of recurrences. MCC patients who produce antibodies to the Merkel cell polyomavirus oncoprotein may benefit from antibody testing in addition to routine imaging surveillance for the early detection of disease recurrence. The clinically available Anti MERKel cell panel (AMERK) is a sensitive tumor marker for Merkel cell polyomavirus positive MCC. Although AMERK is highly sensitive, imaging remains necessary to confirm the location of disease recurrence. MCC exhibits characteristic imaging features, making appropriate imaging modalities, and interpretation important for detection. We present 3 representative patient cases that highlight effective utilization of the AMERK test in addition to imaging for the early detection of MCC recurrence. The rise in the AMERK titer may occur before the disease reaches detectable size on computed tomography scans. Positron emission tomography (PET)-CT can serve as an alternative modality for the early detection of disease. Even subtle abnormalities in ¹⁸F-FDG uptake may be significant if accompanied by an increased AMERK titer. Alternative imaging modalities, such as ⁶⁸Ga-DOTATATE PET-CT and magnetic resonance imaging, can be useful in revealing clinically occult disease in MCC patients. In summary, the AMERK antibody test, alongside imaging, enhances sensitivity in detecting recurrence. By combining these strategies of blood test and imaging, healthcare professionals can identify early signs of MCC recurrence, leading to prompt interventions and improved patient outcomes.

Keywords: 2-deoxy-2-[18F] fluoro-D-glucose (18F-FDG) positron emission tomography; Anti MERKel cell panel (AMERK); Computed tomography; Magnetic resonance imaging; Merkel cell carcinoma; Merkel cell polyomavirus oncoprotein antibody; Tumor biomarkers; [68Ga]-DOTA-Tyr(3)-Thr(8)-octreotate (68Ga-DOTATATE).