D. A. Zambrano1,3, L. I. Ruffolo1, K. M. Jackson1, N. A. Ullman1, K. Pineda-Solis1, M. A. Georger1, B. Belt1, L. De Las Casas2, D. C. Linehan1, E. Galka1 1University Of Rochester,Surgery,Rochester, NY, USA 2University Of Rochester,Pathology,Rochester, NY, USA 3University Of Rochester,School Of Medicine And Dentistry,Rochester, NY, USA
Introduction: Merkel Cell Carcinoma (MCC) is a rare carcinoma of the skin, arising from neuroendocrine cells within the tactile sensory organ. MCC is endemic in regions with high UV exposure, such as equatorial latitudes, but has also been described in less UV exposed regions following infection with Merkel Cell Polyoma Virus. Resection can be curative in early disease, however, many patients recur with disseminated metastases. Here we present a rare metastatic pattern of MCC in two patients with curative resection who developed pancreatic metastases, and were subsequently successfully treated with immunotherapy.
Methods: Following approval by the institutional review board, we conducted a retrospective review of all patients presenting to a tertiary referral center with a diagnosis of MCC. Patient characteristics, demographics, and clinicopathologic data was abstracted. Patient histories were reviewed for presence of distant metastases, location, and treatment. Clinicopathologic outcomes were compared with Student’s T test or Chi-square, non-normally distributed variables were compared with non-parametric statistics as appropriate.
Results: Between 2011-2018 57, patients presented for wide local excision for MCC. Of these, 25 (44%) developed subsequent metastatic recurrence. Patients who developed metastases were more likely to have nodal positive disease on sentinel lymph node biopsy compared to those without recurrence (60% nodal disease vs. 25%, p<0.05). Of patients who presented with metastatic disease, two had localized metastases to the tail of the pancreas which presented 11 and 23 months after resection of the primary tumor. Both of these patients were subsequently treated with single agent immune checkpoint blockade (ICB) (Pembrolizumab). One patient exhibited complete response after two years of ICB therapy which has been discontinued and has no recurrence in two years (Figure 1). The second patient exhibited partial response by RECIST 1.1 criteria (Figure 1) but complete metabolic response by FDG-PET and continues to receive ICB.
Conclusion: Merkel Cell Carcinoma with pancreatic metastasis is a rare but potentially treatable disease. In this case series two patients exhibited excellent response to single agent ICB. Future work in patients with Merkel cell carcinoma will explore the tumor microenvironment in metastatic and primary sites, to delve into predictors of response and mechanisms of ICB resistance.
