Merkel cell carcinoma is an uncommon, aggressive and often fatal skin cancer. It is most commonly seen in areas of the body with greater UV exposure, accounting for approximately 80% of the lesions on head, neck and extremity region. It is a disease of elderly patients and more common in Caucasians and men. Immunosuppression (HIV infection, organ transplantation, chronic lymphocytic leukemia) is also associated with an an increased risk of developing Merkel cell carcinoma. Merkel cell carcinoma has a relatively higher risk of local, regional and distant recurrence irrespective of treatment. The mortality associated with Merkel cell carcinoma at 2 years and 5 years after diagnosis is approximately 30% and 50%, respectively.(1)
The clinical characteristics of Merkel cell carcinoma are indistinctive and it presents as a benign mass and is rarely suspected for at the time of biopsy. Merkel cell carcinoma presents as an asymptomatic, rapidly growing, bluish-red dermal papule or nodule that fair-skinned over a course of weeks to months. It can be easily confused with other common lesions, such as basal cell carcinoma, epidermoid cyst, or amelanotic melanoma. Therefore, the acronym, AEIOU representing asymptomatic, expanding rapidly, immune suppression, older than 50 years and ultraviolet exposure/fair-skinned should be considered for the diagnosis of the tumor. However, the diagnosis is confirmed after a biopsy result.(1)
How Do You Stop Merkel Cell Carcinoma From Spreading?
The various therapies to stop Merkel cell carcinoma from spreading include radiation therapy, chemotherapy and immunotherapy; however, the best treatment for Merkel cell carcinoma is surgical extirpation of the tumor. The surgical management of the early local lesion is done by local excision of the tumor with the inclusion of 1-2 cm of the healthy margins. This is done to prevent recurrence of the tumor as Merkel cell carcinoma has a higher recurrence rate. In areas where tissue sparing is of critical importance, Mohs microscopic surgery may be utilized provided there is no interference with sentinel lymph node biopsy when it is indicated.(2)
In cases with positive sentinel lymph node biopsy, fine needle aspiration and core needle biopsy complete lymph node dissection and/or radiation therapy should be considered. While considering complete lymph node dissection or radiation therapy, it is important to consider the location of lymph node bed as radiation therapy is better tolerated at inguinal nodal basin whereas complete lymph node dissection has lower morbidity for axillary lymph nodes.(2)
Adjuvant radiation therapy is helpful for locoregional control of Merkel cell carcinoma and is associated with decreased recurrence rate; however, it does not affect the overall survival of the patient. In cases where sentinel lymph node biopsy is negative, radiation therapy does not offer any advantage. However, it can be used in locoregional control of inoperable cases.(2)
Although Merkel cell carcinoma is really sensitive to chemotherapy, the response is short-lived and the tumor recurs within 4-15 months. Furthermore, the associated toxicity decreases the overall survival of the patient. The common regimen includes platinum-based products, such as carboplatin or cisplatin with the addition of etoposide.
The other regimen includes cyclophosphamide, doxorubicin, and vincristine.(2)
The treatment for advanced Merkel cell carcinoma is mostly palliative with single-fraction radiation therapy. For locoregional disease high-dose brachytherapy has exceptional results; however, it does not change the overall survival of the patient and further metastases the place.(2)
Immunotherapy is one of the recent emerging therapies for all cancers including Merkel cell carcinoma. Immunotherapy works by reactivation of antitumor cellular immune responses. It is also important to check the viral status of the tumor as negative viral tumors have more mutations and tumor neoantigens. The common immunotherapy agents pembrolizumab, ipilimumab, and intratumoral IL-12 plasmid vaccine are in the trial phase and have shown positive results. Targeted therapies using drugs (idelalisib, pazopanib, cabozantinib, imatinib) to inhibit molecules required for tumor growth and progression are also being investigated in trials for Merkel cell carcinoma.