July 2011

Abscopal Effect in a Patient With Metastatic Merkel Cell Carcinoma Following Radiation Therapy: Potential Role of Induced Antitumor Immunity

Author Affiliations

Author Affiliations: Harvard Radiation Oncology (Dr Cotter) and Dermatology (Dr Collins) Programs, Harvard Medical School, Boston, Massachusetts; Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston (Dr Dunn); and Departments of Dermatology (Drs Sahni and Wang), Radiology (Dr Zukotynski), and Radiation Oncology (Messrs Hansen and O ’Farrell and Drs Ng and Devlin), Brigham & Women's Hospital, Harvard Medical School, Boston.

Arch Dermatol. 2011;147(7):870-872. doi:10.1001/archdermatol.2011.176

A 70-year-old white man presented with a rapidly enlarging nodule on the right upper medial calf. Excisional biopsy revealed Merkel cell carcinoma (MCC). One month after wide local excision and adjuvant radiation therapy (RT) to the right calf and groin, he developed 14 retrograde cutaneous metastases on the right leg that were palpable clinically and fluorodeoxyglucose avid on positron emission tomography/computed tomography imaging. Although 11 lesions on the upper half of the right lower extremity were treated with surface-mold, computer-optimized, high-dose-rate brachytherapy to a total dose of 12 Gy (1200 rad) in 2 equal fractions, no treatment was given to 2 distant lesions on the right ankle (Figure 1A and Figure 2A) and the plantar aspect of the right foot. All lesions, including the 2 untreated lesions, resolved clinically (Figure 1B) and radiographically (Figure 2B) within a few weeks after RT. Treatment response was durable with no recurrence at the right ankle or foot 25 months after brachytherapy when the patient developed visceral metastatic disease. The resolution of the untreated lesions is consistent with the abscopal effect, whereby localized RT induces the regression of tumors at untreated distant sites.1 The abscopal response is extremely rare and has been observed in melanoma as well as hematologic and solid tumors. To our knowledge, this is the first reported case of an abscopal effect in MCC.

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