The Role of Radiation Treatment in Merkel Cell Carcinoma
The Role of Radiation Treatment in Merkel Cell Carcinoma
Merkel cell carcinoma is an aggressive, radiosensitive cutaneous neuroendocrine tumour. In this review, the roles of radiation therapy and chemoradiation in the management of Merkel cell carcinoma are described and discussed, and guidelines for patient management are presented. Radiation treatment may be indicated for definitive (> 55 Gy) or adjuvant (> 50 Gy) treatment of the primary tumour site and for prophylactic (> 50 Gy), adjuvant (> 50 Gy) or definitive (> 55 Gy) treatment of the regional lymph node field. If a patient presents with positive margins after initial biopsy or resection, definitive radiation therapy or chemoradiation may be an alternative to further surgery and, importantly, results in less delay than re-resection followed by adjuvant radiation treatment. Given the rarity of this tumour, patients should be enrolled on prospective databases and clinical trials, and managed in a multidisciplinary clinical setting wherever possible.
Merkel cell carcinoma (MCC) is an aggressive cutaneous tumour that has a predilection for occurring in sun-exposed skin of elderly patients. It is also termed primary cutaneous neuroendocrine carcinoma, based on the ultrastructural finding of dense core granules within the tumour cells and immunohistochemical evidence of neuroendocrine differentiation, similar to Merkel cells of the skin (Fig. 1). Ultraviolet irradiation is the major risk factor for MCC and there is an increased incidence in immunosuppressed patients. Recently it was discovered that a newly identified polyomavirus (termed Merkel cell virus) is clonally integrated into the genome of MCC in the majority of patients. However, the role of the virus in the pathogenesis of MCC remains controversial. MCC is a radiosensitive tumour and, as such, the role of radiation therapy or chemoradiation in this disease is increasing and is becoming better defined. The indications for radiation therapy or chemoradiation range from adjuvant treatment to definitive treatment, through to the palliation of incurable disease.
(Enlarge Image)
Figure 1.
Histological appearance of primary Merkel cell carcinoma of skin at low (a) and high (b) magnification. The tumour cells show immunohistochemical evidence of neuroendocrine differentiation with positive staining for synaptophysin (c).
Abstract and Introduction
Abstract
Merkel cell carcinoma is an aggressive, radiosensitive cutaneous neuroendocrine tumour. In this review, the roles of radiation therapy and chemoradiation in the management of Merkel cell carcinoma are described and discussed, and guidelines for patient management are presented. Radiation treatment may be indicated for definitive (> 55 Gy) or adjuvant (> 50 Gy) treatment of the primary tumour site and for prophylactic (> 50 Gy), adjuvant (> 50 Gy) or definitive (> 55 Gy) treatment of the regional lymph node field. If a patient presents with positive margins after initial biopsy or resection, definitive radiation therapy or chemoradiation may be an alternative to further surgery and, importantly, results in less delay than re-resection followed by adjuvant radiation treatment. Given the rarity of this tumour, patients should be enrolled on prospective databases and clinical trials, and managed in a multidisciplinary clinical setting wherever possible.
Introduction
Merkel cell carcinoma (MCC) is an aggressive cutaneous tumour that has a predilection for occurring in sun-exposed skin of elderly patients. It is also termed primary cutaneous neuroendocrine carcinoma, based on the ultrastructural finding of dense core granules within the tumour cells and immunohistochemical evidence of neuroendocrine differentiation, similar to Merkel cells of the skin (Fig. 1). Ultraviolet irradiation is the major risk factor for MCC and there is an increased incidence in immunosuppressed patients. Recently it was discovered that a newly identified polyomavirus (termed Merkel cell virus) is clonally integrated into the genome of MCC in the majority of patients. However, the role of the virus in the pathogenesis of MCC remains controversial. MCC is a radiosensitive tumour and, as such, the role of radiation therapy or chemoradiation in this disease is increasing and is becoming better defined. The indications for radiation therapy or chemoradiation range from adjuvant treatment to definitive treatment, through to the palliation of incurable disease.
(Enlarge Image)
Figure 1.
Histological appearance of primary Merkel cell carcinoma of skin at low (a) and high (b) magnification. The tumour cells show immunohistochemical evidence of neuroendocrine differentiation with positive staining for synaptophysin (c).