Radiotherapy in the Multidisciplinary Management of Merkel Cell Carcinoma

Abstract

The management of Merkel cell carcinoma (MCC) requires multidisciplinary care for optimal patient outcomes. Radiotherapy (RT) is most commonly used as adjuvant therapy to improve locoregional control in patients with MCC who undergo surgery. Additionally, it can sometimes be used as definitive monotherapy for patients who decline or are not candidates for surgery and as palliative treatment in those with metastatic MCC. This article discusses the indications, treatment considerations, and recommended dose prescriptions for RT in the management of early- and advanced-stage disease. Considerable hope exists that immunotherapy advances will synergize with RT to further enhance clinical outcomes.

An Aggressive Presentation of Merkel Cell Carcinoma: A Case Report

“… 1 , 2 When compared with monotherapy (surgery or radiotherapy), the combination of WLE with adjuvant radiotherapy improved locoregional control and disease-free survival with a statistically significant benefit. 9 , 10 Radiotherapy alone is preferred for locally advanced and unresectable tumors, and chemotherapy appears to be beneficial in metastatic MCC. 10 Although current data suggest that the adjunction of chemotherapy in patients at high risk of recurrence (lymph nodes invasion, tumor >1 cm, and pathological surgical margins) do not improve locoregional control and survival rates, each case of MCC should be evaluated in a multidisciplinary cancer team in order to indicate adjuvant chemotherapy.…”

“… 9 , 10 Radiotherapy alone is preferred for locally advanced and unresectable tumors, and chemotherapy appears to be beneficial in metastatic MCC. 10 Although current data suggest that the adjunction of chemotherapy in patients at high risk of recurrence (lymph nodes invasion, tumor >1 cm, and pathological surgical margins) do not improve locoregional control and survival rates, each case of MCC should be evaluated in a multidisciplinary cancer team in order to indicate adjuvant chemotherapy. 3 , 6 Immunotherapy has revolutionized the management of this orphan disease and preliminary data from non-randomized trials in patients with metastatic or recurrent locoregional MCC, demonstrate that avelumab, an anti-PDL-1 agent and pembrolizumab and nivolumab anti-PD-1 agents improved the rate of prolonged response, compared with cytotoxic therapy.…”

Definitive Radiation Therapy for Merkel Cell Carcinoma Misdiagnosed as a Metastatic Tumor: A Case Report

“…Pathologically, MCC belongs to the family of small round cell tumors. The diagnosis of MCC is made on the basis of detailed IHC analysis of biopsy samples [6]. Positive CK-20 staining is observed in 75-100% of MCC cases, and a paranuclear dot-like staining pattern is typical, whereas CK-20 positivity is rarely observed in small cell carcinoma of the lung and of other organs [1].…”

“…In such situations, 60-66 Gy administered at the conventional fractionation of 1.8 to 2 Gy per treatment is recommended [1]. The clinical target volume typically encompasses the gross tumor with a 3-5 cm margin, and bolus is used to assure sufficient radiation delivery to the full thickness of the skin and underlying fascia [6]. These treatment strategies were applied in the present case.…”

“…MCC presents as a rapidly growing, firm, red to violaceous nodule localized on the skin exposed to ultraviolet (UV) radiation [2]. It is common in patients with suppressed immune status including those undergoing chronic hemodialysis [6][7][8][9]. The incidence of MCC increases markedly in patients aged >70 years, which is attributed to the burden of chronic mutagenic UV exposure and age-associated diminished immuno-surveillance [6].…”