Radiation therapy in the management of Merkel cell carcinoma: current perspectives

An Updated Review of the Biomarkers of Response to Immune Checkpoint Inhibitors in Merkel Cell Carcinoma: Merkel Cell Carcinoma and Immunotherapy

Merkel cell carcinoma (MCC) is primarily a disease of the elderly Caucasian, with most cases occurring in individuals over 50. Immune checkpoint inhibitors (ICI) treatment has shown promising results in MCC patients. Although ~34% of MCC patients are expected to exhibit at least one of the predictive biomarkers (PD-L1, high tumor mutational burden/TMB-H/, and microsatellite instability), their clinical significance in MCC is not fully understood. PD-L1 expression has been variably described in MCC, but its predictive value has not been established yet. Our literature survey indicates conflicting results regarding the predictive value of TMB in ICI therapy for MCC. Avelumab therapy has shown promising results in Merkel cell polyomavirus (MCPyV)-negative MCC patients with TMB-H, while pembrolizumab therapy has shown better response in patients with low TMB. A study evaluating neoadjuvant nivolumab therapy found no significant difference in treatment response between the tumor etiologies and TMB levels. In addition to ICI therapy, other treatments that induce apoptosis, such as milademetan, have demonstrated positive responses in MCPyV-positive MCC, with few somatic mutations and wild-type TP53. This review summarizes current knowledge and discusses emerging and potentially predictive biomarkers for MCC therapy with ICI.

Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immunotherapy for the treatment of nonmelanoma skin cancer

Nonmelanoma skin cancers (NMSCs) are some of the most commonly diagnosed malignancies. In general, early-stage NMSCs have favorable outcomes; however, a small subset of patients develop resistant, advanced, or metastatic disease, or aggressive subtypes that are more challenging to treat successfully. Recently, immune checkpoint inhibitors (ICIs) have been approved by the US Food and Drug Administration (FDA) for the treatment of Merkel cell carcinoma (MCC), cutaneous squamous cell carcinoma (CSCC), and basal cell carcinoma (BCC). Although ICIs have demonstrated activity against NMSCs, the routine clinical use of these agents may be more challenging due to a number of factors including the lack of predictive biomarkers, the need to consider special patient populations, the management of toxicity, and the assessment of atypical responses. With the goal of improving patient care by providing expert guidance to the oncology community, the Society for Immunotherapy of Cancer (SITC) convened a multidisciplinary panel of experts to develop a clinical practice guideline (CPG). The expert panel drew on the published literature as well as their own clinical experience to develop recommendations for healthcare professionals on important aspects of immunotherapeutic treatment for NMSCs, including staging, biomarker testing, patient selection, therapy selection, post-treatment response evaluation and surveillance, and patient quality of life (QOL) considerations, among others. The evidence- and consensus-based recommendations in this CPG are intended to provide guidance to cancer care professionals treating patients with NMSCs.

Survival Benefit of Guideline-Concordant Postoperative Radiation for Local Merkel Cell Carcinoma

BACKGROUND

Postoperative radiation therapy (RT) for early-stage Merkel Cell Carcinoma (MCC) decreases the risk of locoregional recurrence and improve overall survival. However, concordance with RT guidelines is unknown.

MATERIALS AND METHODS

The National Cancer Database was queried for stage I/II MCC patients receiving surgical intervention from 2006-2017. The cohort was stratified by patients who had and did not have indication(s) for adjuvant RT of the primary tumor site based on National Comprehensive Cancer Network guidelines. We captured the use of RT, patient demographics, socioeconomic characteristics, and clinical characteristics. Logistic regression, Kaplan-Meier method, and propensity score weighted Cox proportional hazards model examined associations and survival benefits of RT.

RESULTS

2,330 stage I/II MCC patients underwent surgical intervention. 1,858 (79.7%) met National Comprehensive Cancer Network criteria for RT of the primary tumor site, of which 1,062 (57.2%) received RT. 472 (20.3%) did not meet criteria for RT, of which 203 (43.0%) received RT. Five-year overall survival advantage was identified for patients who received RT when it was indicated (P < 0.003). There was no evidence of overall survival advantage when patients received guideline-discordant RT (P = 0.478).

CONCLUSIONS

Surgical resection with adjuvant RT of the primary tumor site has an overall survival benefit for local MCC when patients meet criteria for RT. This study found a group who received guideline-discordant RT with no survival advantage. Further investigation is warranted to identify the socio-demographic and oncologic reasons for guideline discordance in the treatment of MCC for both under- and over-treatment.

Development and Implementation of an Online Adaptive Stereotactic Body Radiation Therapy Workflow for Treatment of Intracardiac Metastasis

Cardiac metastases pose clinical challenges for radiation oncologists given the need to balance the benefit of local therapy against the risks of cardiac toxicity in the setting of cardiac motion, respiratory motion, and nearby organs at risk. Stereotactic magnetic resonance-guided adaptive radiation therapy has recently become more commonly used, conferring benefits in tumor visualization for setup, real-time motion management monitoring, and enabling plan adaptation for daily changes in tumor and/or normal tissues. Given these benefits, we developed and implemented a workflow for local treatment of metastatic disease within the heart using stereotactic magnetic resonance-guided adaptive radiation therapy.

How we treat Merkel cell carcinoma: within and beyond current guidelines

Merkel cell carcinoma (MCC) is an aggressive skin cancer associated with a high risk of local recurrence and distant metastasis. Optimal care of this potentially life-threatening cancer is critical but challenging because: physicians are often unfamiliar with its management due to rarity, and MCC management remains controversial, in part because it is rapidly evolving across multiple specialties. While guidelines offer a broad overview of management, they are often not sufficient when making decisions for individual patients. Herein, we present a literature review as well as practical approaches adopted at our institutions for staging, surveillance and therapy of MCC. Each of these areas are discussed in light of how they can be appropriately customized for prevalent but challenging situations. We also provide representative examples of MCC patient scenarios and how they were managed by a multidisciplinary team to identify suitable evidence-based, individualized treatment plans.

Merkel cell carcinoma (MCC) is a skin cancer with a high risk of recurrence and distant spread. Optimal care of this cancer is important. However, management is challenging because it is rare and its treatment is continuously evolving across multiple specialties. While treatment guidelines offer a broad overview of management, they are often not detailed enough to provide appropriate patient-specific assistance. Herein, we present a review of recent studies and our suggestions relevant to MCC staging, surveillance and treatment options. Each of these areas are discussed in light of how they can be appropriately customized for challenging situations often encountered by practitioners. We also provide representative examples of MCC patient scenarios and how they were managed by a multidisciplinary team to identify evidence-based, individualized treatment plans.

Demographic features and changing incidence and presentation of Merkel cell carcinoma in a retrospective single-center case series

Merkel cell carcinoma (MCC) is an uncommon aggressive cutaneous neuroendocrine tumor with high mortality. The purpose of this study is to describe the clinical correlates of MCC and identify changing trends over time using a retrospective chart review of 113 cases in a single tertiary center pathology database from 1997 to 2015. MCC occurred mostly in the elderly (median age 77 years), more often in males (n = 60, 53%), was most commonly located on the head and neck region (n = 63, 56%), and most commonly presented on the left side of the body (n = 59, 52%). Overall, there was an increase in MCC diagnoses per year from 1997 to 2015, with 2.3 times more cases diagnosed in the last 3 years of the study period than in the first 3 years. Furthermore, cases diagnosed after 2008 were more likely to occur in younger patients, less than or equal to 77 years of age (OR 2.32, 95% CI 1.08, 4.97, p = 0.04). The median age of diagnosis among females was 76 years and among males was 74 years. There was no change in the overall age of diagnosis among men and a decrease in age of diagnosis among females during the study. There was an overall increase in the MCC cases diagnosed among women, and a slight increase in the proportion of females affected by MCC throughout the course of the study. This retrospective case series elucidates MCC epidemiologic characteristics and describes how incidence, sex, and age at diagnosis have changed over the course of the study.

Merkel Cell Polyomavirus and Merkel Cell Carcinoma

Viruses are the cause of approximately 15% of all human cancers. Both RNA and DNA human tumor viruses have been identified, with Merkel cell polyomavirus being the most recent one to be linked to cancer. This virus is associated with about 80% of Merkel cell carcinomas, a rare, but aggressive cutaneous malignancy. Despite its name, the cells of origin of this tumor may not be Merkel cells. This review provides an update on the structure and life cycle, cell tropism and epidemiology of the virus and its oncogenic properties. Putative strategies to prevent viral infection or treat virus-positive Merkel cell carcinoma patients are discussed.

Definitive Radiotherapy for Locally Advanced Merkel Cell Carcinoma of the Head and Neck Region: A Case Report

 

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine malignancy of skin origin. It is most commonly managed with upfront surgical resection which is then followed by radiotherapy as soon as possible postoperatively. Radiotherapy alone has been used in inoperable cases and in cases of patient preference to omit surgical management. MCC is a very radiosensitive disease, and an ideal location for definitive radiotherapy is the head and neck region (which represents the majority of cases), where resection often leads to reduced outcomes given the number of critical structures in the region and the inability of surgery to achieve the excision margins required for the aggressive nature of the disease without leading to severely impacted cosmesis and function. This case study looks at an elderly woman who was treated with definitive dose fractionation (to a total dose of 60 Gray in 30 fractions) radiotherapy to the head and neck region for Stage III, T1N2M0 disease, following rapid loco-regional relapse after surgical wide local excision. Two years postdefinitive radiotherapy, she has had complete loco-regional control both clinically and radiologically.

Contemporary Topics in Radiation Medicine: Skin Cancer

Radiation plays an important role in the management of a variety of skin cancers. This article discusses the role of radiation in the treatment of cutaneous squamous cell carcinoma, basal cell carcinoma, Merkel cell carcinoma, cutaneous T-cell lymphoma, and B-cell lymphomas.

Combined radio-immunotherapy leads to complete clinical regression of stage IV Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine tumour of the skin. While localised disease carries an overall favourable prognosis, metastatic disease is associated with poor clincal outcomes. Most cases of metastatic MCC are managed with systemic chemotherapy or immunotherapy, though 5-year survival for these patients remains a dismal 17%. Here, we present the case of a 79-year-old man with MCC of the right ear with metastases to regional lymph nodes, ipsilateral parotid gland and thoracic spine. He was treated with a combination of first-line radiotherapy and concurrent immune checkpoint inhibition (avelumab), which led to complete clinical regression of disease with minimal adverse effects. This observation suggests that combined radio-immunotherapy warrants larger-scale investigation for use in patients with unresectable MCC.

Merkel Cell Carcinoma: Therapeutic Update and Emerging Therapies

Merkel cell carcinoma (MCC) is a rare but highly aggressive neuroendocrine skin cancer whose incidence has almost doubled in recent decades. Risk factors for MCC include age > 65 years, immunosuppression, sun exposure and infection by Merkel cell polyomavirus. MCC usually presents as rapidly growing, firm, red to violaceous nodule localized on the sun-exposed skin. Surgery followed by radiation therapy is considered to be the first-line treatment for primary or loco-regional MCC in order to prevent recurrences and lymph node metastasis, while chemotherapy has always been used to treat advanced forms. However, responses to chemotherapy are mostly of short duration, and the associated clinical benefit on overall survival is still unclear. The use of checkpoint inhibitors (CPIs) has shown good results in the treatment of advanced MCC and, consequently, CPIs are considered emerging immunotherapeutic options for these patients, although there are still no standardized treatments for patients with metastatic disease. Here we present a complete overview of the different possibilities for the treatment of MCC according to the stage of the disease, focusing on the emerging immunotherapies used for treating advanced MCC.

Merkel cell carcinoma: Epidemiology, pathogenesis, diagnosis and therapy

Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer with a neuroendocrine phenotype. Incidence varies according to the geographic regions but is overall increasing. Different risk factors have been identified namely advanced age, immunosuppression, and ultraviolet light exposure. An association between MCC and polyomavirus infection is known. However, the exact mechanism that leads to carcinogenesis is yet to be fully understood. Surgery when feasible is the recommended treatment for localized disease, followed by adjuvant radiation or chemoradiation. In the metastatic setting, chemotherapy has been the standard treatment. However, two recently published trials with immune checkpoint inhibitors in first and second line showed promising results with a tolerable safety profile and these might become the standard therapy shortly. Somatostatin receptors are expressed in many MCC but such expression is not associated with disease severity. Presently there are no biomarkers predictive of response that could help to better select patients to these new therapies, and additional research is essential.

Sentinel lymph node biopsy in Merkel cell carcinoma: The Mayo Clinic experience of 150 patients

BACKGROUND

Merkel cell carcinoma (MCC) is a rare cutaneous malignancy of neuroendocrine origin with a high propensity for lymph node metastasis. Sentinel lymph node (SLN) status is important for accurate staging; however, the optimal treatment following SLN biopsy, regardless of nodal status, remains unclear.

METHODS

150 patients with MCC who underwent SLN biopsy from 1995 to 2011 at 3 Mayo Clinic sites were reviewed.

RESULTS

Of 150 patients with MCC who underwent SLN biopsy, 39 (26%) were positive and 111 (74%) were negative. There was no significant difference between the sex, age, tumor location, or size of primary in the positive and negative SLN groups. While there was no difference in the cumulative incidence of any regional recurrence between SLN groups, the rate of in-transit recurrences was significantly higher in patients with a positive SLN (p = 0.022). The disease-specific survival for MCC was 97.0%, 82.4%, and 82.4% at 1, 3, and 5 years with a positive SLN and 99.0%, 94.9%, and 86.8% with a negative SLN (p = 0.31). Among those alive at last follow up, the median follow up was 3.8 years (IQR, 2.1-8.4) and 2.9 years (IQR, 1.8-6.1) for positive and negative SLN cohorts respectively.

CONCLUSIONS

Occult nodal metastasis is common in MCC(26%). No tumor or patient characteristics were identified to predict SLN positivity. Patients with a positive SLN have a higher risk of in-transit recurrence and may benefit from adjuvant radiation with inclusion of the in-transit field in amenable cases. When patients with a positive SLN receive additional treatment to the at-risk nodal basin, both OS and DSS are similar to patients with a negative SLN.

Merkel Cell Polyomavirus: A New DNA Virus Associated with Human Cancer

Merkel cell polyomavirus (MCPyV or MCV) is a novel human polyomavirus that has been discovered in Merkel cell carcinoma (MCC), a highly aggressive skin cancer. MCPyV infection is widespread in the general population. MCPyV-associated MCC is one of the most aggressive skin cancers, killing more patients than other well-known cancers such as cutaneous T-cell lymphoma and chronic myelogenous leukemia (CML). Currently, however, there is no effective drug for curing this cancer. The incidence of MCC has tripled over the past two decades. With the widespread infection of MCPyV and the increase in MCC diagnoses, it is critical to better understand the biology of MCPyV and its oncogenic potential. In this chapter, we summarize recent discoveries regarding MCPyV molecular virology, host cellular tropism, mechanisms of MCPyV oncoprotein-mediated oncogenesis, and current therapeutic strategies for MCPyV-associated MCC. We also present epidemiological evidence for MCPyV infection in HIV patients and links between MCPyV and non-MCC human cancers.

Merkel Cell Carcinoma Therapeutic Update

OPINION STATEMENT

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine tumor of the skin. Early-stage disease can be cured with surgical resection and radiotherapy (RT). Sentinel lymph node biopsy (SLNB) is an important staging tool, as a microscopic MCC is frequently identified. Adjuvant RT to the primary excision site and regional lymph node bed may improve locoregional control. However, newer studies confirm that patients with biopsy-negative sentinel lymph nodes may not benefit from regional RT. Advanced MCC currently lacks a highly effective treatment as responses to chemotherapy are not durable. Recent work suggests that immunotherapy targeting the programmed cell death receptor 1/programmed cell death ligand 1 (PD-1/PD-L1) checkpoint holds great promise in treating advanced MCC and may provide durable responses in a portion of patients. At the same time, high-throughput sequencing studies have demonstrated significant differences in the mutational profiles of tumors with and without the Merkel cell polyomavirus (MCV). An important secondary endpoint in the ongoing immunotherapy trials for MCC will be determining if there is a response difference between the virus-positive MCC tumors that typically lack a large mutational burden and the virus-negative tumors that have a large number of somatic mutations and predicted tumor neoantigens. Interestingly, sequencing studies have failed to identify a highly recurrent activated driver pathway in the majority of MCC tumors. This may explain why targeted therapies can demonstrate exceptional responses in case reports but fail when treating all comers with MCC. Ultimately, a precision medicine approach may be more appropriate for treating MCC, where identified driver mutations are used to direct targeted therapies. At a minimum, stratifying patients in future clinical trials based on tumor viral status should be considered as virus-negative tumors are more likely to harbor activating driver mutations.