Patterns of distant metastases in 215 Merkel cell carcinoma patients: Implications for prognosis and surveillance

Avelumab as second-line or later treatment in patients with metastatic Merkel cell carcinoma: Analysis of real-world outcomes in France using the CARADERM database linked to the French national healthcare database

AIM

Avelumab has been approved worldwide for treatment of metastatic Merkel cell carcinoma (mMCC), a rare and aggressive skin cancer. This study evaluated outcomes in patients with mMCC in France who received avelumab as second-line or later (2L+) treatment in routine clinical practice.

METHODS

This retrospective, noninterventional study evaluated all patients diagnosed with mMCC using two databases: CARADERM (French national database of rare dermatological cancers) and SNDS (national healthcare database), identified via probabilistic linkage. Eligible patients initiated avelumab as 2L+ treatment between August 2016 and December 2019 and were followed for 24 months. The primary endpoint was overall survival (OS) at 24 months.

RESULTS

Overall, 180 patients who received 2L+ avelumab were identified (112 from CARADERM, 68 after SNDS linkage). Median age at diagnosis was 74.0 years and 177 (98.3 %) had received chemotherapy alone as first-line treatment. Median follow-up was 13.1 months. Median OS from start of avelumab was 14.6 months (95 % CI, 9.9-21.3) in the overall population, 15.9 months (95 % CI, 8.6-28.3) in CARADERM patients, and 13.3 months (95 % CI, 6.7-19.1) in non-CARADERM patients. OS rates at 12 and 24 months were 53.8 % (95 % CI, 46.2 %-60.8 %) and 40.5 % (95 % CI, 33.2 %-47.6 %), respectively. In evaluable patients (CARADERM database), median progression-free survival was 3.6 months (95 % CI, 2.7-7.5) and the objective response rate was 55.3 % (95 % CI, 45.3-65.4), including complete response in 31.9 %.

CONCLUSIONS

Real-world outcomes with 2L+ avelumab treatment for mMCC are consistent with clinical trial findings, supporting the recommendation of avelumab as a standard of care.

Mast cell density in Merkel cell carcinoma and its correlation with prognostic features and MCPyV status: a pilot study

Merkel cell carcinoma (MCC) is a rare, highly aggressive, primitive neuroendocrine carcinoma of the skin, the origin of which is not yet fully understood. Numerous independent prognostic factors have been investigated in an attempt to understand which are the most important parameters to indicate in the histological diagnostic report of MCC. Of these, mast cells have only been studied in one paper before this one. We present a retrospective descriptive study of 13 cases of MCC, received at the Department of Pathology over a 20-year period (2003-2023 inclusive) on which we performed a study using whole-slide (WSI) morphometric analysis scanning platform Aperio Scanscope CS for the detection and spatial distribution of mast cells, using monoclonal anti-tryptase antibody and anti-CD34 monoclonal antibody to study the density of microvessels. In addition, we analyzed MCPyV status with the antibody for MCPyV large T-antigen (Clone CM2B4). We found statistically significant correlation between mast cell density and local recurrence/distant metastasis/death-of-disease (p = 0.008). To our knowledge, we firstly reported that MCPyV ( -) MCC shows higher mast cells density compared to MCPyV ( +) MCC, the latter well known to be less aggressive. Besides, the median vascular density did not show no significant correlation with recurrence/metastasis/death-of-disease, (p = 0.18). Despite the small sample size, this paper prompts future studies investigating the role of mast cell density in MCC.

A SEER program study of survival trends in Merkel cell carcinoma of the eyelid: 2000-2019

PURPOSE

Merkel cell carcinoma of the eyelid (MCCE) is a rare yet aggressive neuroendocrine tumour associated with significant morbidity and mortality. This study aimed to investigate survival trends and demographic factors related to MCCE, 2000-2019, using the Surveillance, Epidemiology, and End Results (SEER) Program.

METHODS

Cases were analysed by demographic parameters, disease properties, and survival. Statistical analyses were performed via a dedicated computerized software package.

RESULTS

A total 349 cases of MCCE were identified, accounting for 2% of all MCC cases in the United States during that time. Of note, the incidence of MCCE remained stable over the study period (p = .35). Female patients accounted for 56% of the cases, and males for 44%. White patients accounted for 90.8% of the the cases, and Black patients for 2.9%. MCCE incidence increased with age, with the majority of patients age 85+ (p < .05). Incidence was greatest in metropolitan areas and among those with median incomes >$75,000/year. Income correlated with likelihood of MCCE diagnosis (p < .05). Analysis of 5-year survival data showed 20% of the patients died due to MCCE within 5 years of diagnosis. Of these, the majority died within one year of diagnosis.

CONCLUSIONS

Consistent with previous reports, most patients were white, female, and age 85+.Incidence correlated with metropolitan environments and median income. While most patients did not die from MCCE, majority of recorded deaths occurred within one year of diagnosis.

Patterns of initial distant metastases in 151 patients undergoing surveillance for treated Merkel cell carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) is associated with high rates of recurrence and distant metastatic progression. Current guidelines for surveillance imaging are not evidence based. Better characterization of the pattern of distant metastatic spread will better inform surveillance and facilitate earlier detection of metastases.

OBJECTIVES

This retrospective study aimed to assess potential relationships between primary tumour site and site of initial distant metastasis, time to distant metastasis, overall survival (OS) and MCC-specific death (MSD).

METHODS

Patients with local or regional (Stage I-III) disease who were treated with curative intent and progressed to Stage IV were included in this study (n = 151). Fisher's exact test was used to assess differences in patterns of initial distant metastases based on primary tumour site. Time to initial distant metastasis was calculated from date of MCC diagnosis. OS and MSD were calculated from date of initial distant metastasis to date of death from any or MCC-related causes, respectively.

RESULTS

Of 151 patients included in analysis, 89 (58.9%) had a single initial distant metastatic site, and 62 (41.1%) had multiple sites. Patients with upper limb primary tumours were significantly less likely to develop distant lymph node or liver metastases (p = 0.02 and 0.04, respectively). Median time to distant metastasis was 11 months (IQR 6.7-17.9 months). Median OS was 15.3 months, and was shorter for patients with liver (7.0 months, p = 0.0004) or bone metastases (8.9 months, p < 0.0001). Using skin/soft tissue metastasis as a reference group, patients with multiple metastatic sites had significantly higher hazards of MSD (HR = 3.46 univariate, 3.77 multivariate analysis). Time to distant metastasis, OS and MSD did not differ by viral status.

CONCLUSION

Sites of initial distant metastasis are related to primary tumour sites and survival outcomes. Because patients often have multiple initial metastases, full-body cross-sectional rather than region-specific imaging may facilitate earlier detection of metastatic disease.

Moderne Diagnostik und Therapie des Merkelzellkarzinoms

Das Merkelzellkarzinom (MCC) ist ein seltener, aggressiver Hauttumor mit epithelialer und neuroendokriner Differenzierung, dessen Inzidenz in den letzten Jahrzehnten deutlich zugenommen hat. Risikofaktoren sind fortgeschrittenes Lebensalter, heller Hauttyp, UV‐Exposition und Immunsuppression. Pathogenetisch wird ein durch das Merkelzell‐Polyomavirus (MCPyV) hervorgerufener Typ von einem UV‐induzierten Typ mit hoher Tumormutationslast unterschieden.

Klinisch präsentiert sich das MCC als meist schmerzloser, schnell wachsender, rötlich‐violetter Tumor mit glänzender Oberfläche, der bevorzugt im Kopf‐Hals‐Bereich und an den distalen Extremitäten lokalisiert ist. Eine sichere Diagnose kann nur anhand histologischer und immunhistochemischer Merkmale gestellt werden. Bei Erstdiagnose weisen 20%–26% der Patienten lokoregionäre Metastasen und 8%–14% Fernmetastasen auf, weshalb eine Ausbreitungsdiagnostik unabdingbar ist. Bei fehlenden klinischen Hinweisen auf Metastasen wird eine Sentinel‐Lymphknotenbiopsie empfohlen.

Wesentliche Säulen der Therapie sind die Operation, die adjuvante oder palliative Strahlentherapie und in fortgeschrittenen inoperablen Stadien die medikamentöse Tumortherapie. Die Einführung von Immuncheckpoint‐Inhibitoren führte zu einem Paradigmenwechsel, da sich hiermit ein wesentlich langfristigeres Ansprechen und bessere Überlebensraten als mit Chemotherapie erreichen lassen. Zur Therapie des metastasierten MCC ist in Deutschland der PD‐L1‐Inhibitor Avelumab zugelassen, aber auch die PD‐1‐Antikörper Pembrolizumab und Nivolumab werden mit Erfolg eingesetzt. Adjuvante und neoadjuvante Therapiekonzepte, Immunkombinationstherapien und zielgerichtete Therapien als Monotherapie oder in Kombination mit Immuncheckpoint‐Inhibitoren befinden sich in klinischer Prüfung.

Modern diagnostics and treatment of Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer with epithelial and neuroendocrine differentiation, the incidence of which has increased substantially during the last decades. Risk factors include advanced age, fair skin type, UV exposure, and immunosuppression. Pathogenetically, a type caused by the Merkel cell polyomavirus is distinguished from a UV-induced type with a high tumor mutational burden. Clinically, MCC presents as a mostly painless, rapidly growing, reddish-violet tumor with a shiny surface, which is preferentially localized in the head-neck region and at the distal extremities. A reliable diagnosis can only be made based on histological and immunohistochemical features. At initial diagnosis, 20-26% of patients show locoregional metastases and 8-14% distant metastases, making staging examinations indispensable. If there is no clinical evidence of metastases, a sentinel lymph node biopsy is recommended. Essential columns of therapy are surgery, adjuvant or palliative radiotherapy and, in advanced inoperable stages, medicamentous tumor therapy. The introduction of immune checkpoint inhibitors has led to a paradigm shift, as they provide a considerably longer duration of response and better survival rates than chemotherapy. The PD-L1 inhibitor avelumab is approved for treatment of metastatic MCC in Germany, but the PD-1 antibodies pembrolizumab and nivolumab are also used with success. Adjuvant and neoadjuvant treatment concepts, immune combination therapies and targeted therapies as monotherapy or in combination with immune checkpoint inhibitors are in the clinical trial phase.

Integrative analysis reveals therapeutic potential of pyrvinium pamoate in Merkel cell carcinoma

Merkel Cell Carcinoma (MCC) is a highly aggressive neuroendocrine cutaneous malignancy arising from either ultraviolet-induced mutagenesis or Merkel cell polyomavirus (MCPyV) integration. It is the only known neuroendocrine tumor (NET) with a virus etiology. Despite extensive research, our understanding of the molecular mechanisms driving the transition from normal cells to MCC remains limited. To address this knowledge gap, we assessed the impact of inducible MCPyV T antigens into normal human fibroblasts by performing RNA sequencing. Our findings suggested that the WNT signaling pathway plays a critical role in the development of MCC. To test this model, we bioinformatically evaluated various perturbagens for their ability to reverse the MCC gene expression signature and identified pyrvinium pamoate, an FDA-approved anthelminthic drug known for its anti-tumor potential in multiple cancers. Leveraging transcriptomic, network, and molecular analyses, we found that pyrvinium effectively targets multiple MCC vulnerabilities. Specifically, pyrvinium not only reverses the neuroendocrine features of MCC by modulating canonical and non-canonical WNT signaling pathways but also inhibits cancer cell growth by activating the p53-mediated apoptosis pathway, disrupting mitochondrial function, and inducing endoplasmic reticulum (ER) stress. Pyrvinium also effectively inhibits tumor growth in an MCC mouse xenograft model. These findings offer new avenues for the development of therapeutic strategies for neuroendocrine cancer and highlight the utility of pyrvinium as a potential treatment for MCC.

A review of Merkel cell carcinoma

ABSTRACT

Merkel cell carcinoma (MCC) is a rare and aggressive type of metastatic, nonmelanoma skin cancer derived from Merkel cells in the epidermis. MCC can be induced by sun exposure or via Merkel cell polyomavirus (MCV) gene expression. MCV is found in most patients with MCC and is associated with a lower recurrence rate of MCC. MCC has a wide range of clinical presentations that make diagnosis challenging. Histologic examination is performed using unique markers to differentiate it from other diagnoses. This article reviews the pathogenesis, clinical presentation, histopathology, differential diagnosis, and treatment of MCC.

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.

Large Intestinal Obstruction and Perforation From Metastatic Merkel Cell Carcinoma: A Case Report

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine neoplasm of the skin that has a high propensity to metastasize. Abdominal metastases of MCC have been described previously though these are typically regional with nodal spread. We report the case of a 60-year-old man with a history of left upper extremity MCC who had resection, radiation therapy, and immunotherapy. He ultimately developed large bowel obstruction from metastatic intraperitoneal implants. A 6 cm mass at the descending colon was biopsied and proven to be metastatic MCC. The tumor eroded through the wall of the colon and perforated, requiring emergent colectomy for septic shock. Herein, we describe the first case of colonic perforation secondary to metastatic MCC. This case illustrates the importance of expedient and multifactorial management of patients with rapidly growing metastatic colonic tumors that are at risk for perforation.

Case report: Metastasis of Merkel cell carcinoma in the small intestine

Merkel cell carcinoma is a rare primary neuroendocrine malignant neoplasm of the skin, which recurs in about 40 % of cases. The main factors are Merkel cell polyomavirus (MCPyV) and mutations caused by ultraviolet radiation [Paulson, 2018]. In this study, we report a case of Merkel cell carcinoma with metastasis to the small intestine. In a 52-year-old woman, a subcutaneous formation of a nodule up to 2.0 cm in diameter was detected during the examination. This neoplasm was removed and sent for histological analysis. Dot-like expression of CK pan, CK 20, chromogranin A, and Synaptophysin was observed in tumor cells, and Ki-67 in 40 % of tumor cells. There is no reaction in tumor cells to CD 45, CK 7, TTF 1, and S100. The morphological picture corresponded to Merkel cell carcinoma. A year later, the patient underwent surgery for intestinal obstruction. The pathohistological changes and immunophenotype of the small bowel tumor were consistent with Merkel cell carcinoma metastasis.

Current and preclinical treatment options for Merkel cell carcinoma

INTRODUCTION

Merkel cell carcinoma (MCC) is a rare, highly aggressive form of skin cancer with neuroendocrine features. The origin of this cancer is still unclear, but research in the last 15 years has demonstrated that MCC arises via two distinct etiologic pathways, i.e. virus and UV-induced. Considering the high mortality rate and the limited therapeutic options available, this review aims to highlight the significance of MCC research and the need for advancement in MCC treatment.

AREAS COVERED

With the advent of the immune checkpoint inhibitor therapies, we now have treatment options providing a survival benefit for patients with advanced MCC. However, the issue of primary and acquired resistance to these therapies remains a significant concern. Therefore, ongoing efforts seeking additional therapeutic targets and approaches for MCC therapy are a necessity. Through a comprehensive literature search, we provide an overview on recent preclinical and clinical studies with respect to MCC therapy.

EXPERT OPINION

Currently, the only evidence-based therapy for MCC is immune checkpoint blockade with anti-PD-1/PD-L1 for advanced patients. Neoadjuvant, adjuvant and combined immune checkpoint blockade are promising treatment options.

Detection of Merkel Cell Polyomavirus (MCPyV) DNA and Transcripts in Merkel Cell Carcinoma (MCC)

Merkel cell polyomavirus (MCPyV) is the etiological agent of the majority of Merkel cell carcinoma (MCC): a rare skin tumor. To improve our understanding of the role of MCPyV in MCCs, the detection and analysis of MCPyV DNA and transcripts were performed on primary tumors and regional lymph nodes from two MCC patients: one metastatic and one non-metastatic. MCPyV-DNA was searched by a quantitative polymerase chain reaction (qPCR), followed by the amplification of a Large T Antigen (LTAg), Viral Protein 1 (VP1) and Non-Coding Control Region (NCCR). LTAg and VP1 transcripts were investigated by reverse-transcription PCR (RT-PCR). Viral integration was also studied, and full-length LTAg sequencing was performed. qPCR revealed that the primary tumor of both patients and the lymph node of one patient was positive for the small t-antigen, with an average value of 7.0 × 10² copies/µg. The same samples harbored LTAg, NCCR and VP1 DNA. Sequencing results showed truncated LTAg with the conserved retinoblastoma (Rb) protein binding motif and VP1 and NCCR sequences identical to the MCC350 strain. RT-PCR detected LTAg but not VP1 transcripts. The MCPyV genome was integrated into the primary tumor of both patients. The results confirmed the connection between MCPyV and MCC, assuming integration, LTAg truncation and Rb sequestration as key players in MCPyV-mediated oncogenesis.

An Extraordinary Cause of Colonic Obstruction: Merkel Cell Carcinoma of Unknown Primary

Merkel cell carcinoma is an aggressive and rare neuroendocrine skin cancer with documented metastases to the liver, lungs, and, seldom, the gastrointestinal tract. Metastases to the colon are rare but are seen with primary skin lesions or recurrent disease. Presented is a patient with large bowel obstruction secondary to a large hepatic flexure mass. Pathologic workup revealed Merkel cell carcinoma, and a dermatologic evaluation did not identify a primary cutaneous lesion. This is the first reported case of Merkel cell carcinoma of unknown primary presenting as large bowel obstruction.

S2k Guideline - Merkel cell carcinoma (MCC, neuroendocrine carcinoma of the skin) - Update 2022

Merkel cell carcinoma (MCC, ICD-O M8247/3) is a rare, malignant, primary skin tumor with epithelial and neuroendocrine differentiation. The tumor cells share many morphologic, immunohistochemical, and ultrastructural features with cutaneous Merkel cells. Nevertheless, the cell of origin of MCC is unclear. MCC appears clinically as a reddish to purple spherical tumor with a smooth, shiny surface and a soft to turgid, elastic consistency, usually showing rapid growth. Spontaneous and often complete regressions of the tumor are observed. These likely immunologically-mediated regressions explain the cases in which only lymph node or distant metastases are found at the time of initial diagnosis and why the tumor responds very well to immunomodulatory therapies even at advanced stages. Due to its aggressiveness, the usually given indication for sentinel lymph node biopsy, the indication of adjuvant therapies to be evaluated, as well as the complexity of the necessary diagnostics, clinical management should already be determined by an interdisciplinary tumor board at the time of initial diagnosis.

Merkel Cell Carcinoma: An Update and Review

Merkel cell carcinoma (MCC) is a rare, very aggressive skin cancer with a high mortality rate and a high tendency of metastatic spread [...].

Management and Prognosis of Cardiac Metastatic Merkel Cell Carcinoma: A Case-Control Study and Literature Review

Merkel cell carcinoma (MCC), an aggressive neuroendocrine skin cancer, has a high rate (20%) of distant metastasis. Within a prospective registry of 582 patients with metastatic MCC (mMCC) diagnosed between 2003-2021, we identified 9 (1.5%) patients who developed cardiac metastatic MCC (mMCC). We compared overall survival (OS) between patients with cardiac and non-cardiac metastases in a matched case-control study. Cardiac metastasis was a late event (median 925 days from initial MCC diagnosis). The right heart was predominantly involved (8 of 9; 89%). Among 7 patients treated with immunotherapy, 6 achieved a complete or partial response of the cardiac lesion. Among these 6 responders, 5 received concurrent cardiac radiotherapy (median 20 Gray) with immunotherapy; 4 of 5 did not have local disease progression or recurrence in the treated cardiac lesion. One-year OS was 44%, which was not significantly different from non-cardiac mMCC patients (45%, p = 0.96). Though it occurs relatively late in the disease course, cardiac mMCC responded to immunotherapy and/or radiotherapy and was not associated with worse prognosis compared to mMCC at other anatomic sites. These results are timely as cardiac mMCC may be increasingly encountered in the era of immunotherapy as patients with metastatic MCC live longer.

Treatment and survival outcomes in metastatic Merkel cell carcinoma: Analysis of 2010 patients from the SEER database

INTRODUCTION

Merkel cell carcinoma (MCC) is an aggressive cutaneous cancer that frequently compromises the lymph nodes (LN) and distal organs. We sought to describe clinical and demographic characteristics of affected patients, analyze risk factors for LN compromise, metastasis, and death, and evaluate their impact on survival.

MATERIALS AND METHODS

Patients with MCC were retrieved from the SEER database. Demographic, clinical and treatment data were analyzed. Logistic and Cox proportional hazard regression were used to analyze risk factors. Survival analysis was done with the Kaplan-Meier method.

RESULTS

A total of 2010 patients were included, among which 288 (14.33%) had distant metastases at diagnosis. LN involvement occurred in 45.8% and 20.1% of patients with and without distant metastasis, respectively. Males were more likely to present LN compromise (OR = 1.33, p<0.001). Tumors >10 mm showed a significantly higher risk for LN involvement and distant metastasis, with those >20 mm showing the highest risk (OR = 2.76 p<0.001 and OR = 8.88 p<0.001 respectively). Location of the tumor in the trunk was a protective factor for overall death (OR = 0.27), while LN compromise was a risk factor (OR = 3.12). Only history of previous malignancy significantly affected disease-specific death (OR = 0.32, p = 0.01). One-year survival was 79.7% and 38.2% for patients with regional LN disease and distant metastasis, respectively.

CONCLUSION

MCC is an aggressive cancer with high rates of LN involvement and distant metastases. Male gender and tumor size were risk factors for regional LN and metastatic disease. Tumor location in the trunk decrease the risk of overall death, while LN involvement increased it.

Current In Vitro and In Vivo Models to Study MCPyV-Associated MCC

Merkel cell polyomavirus (MCPyV) is the only human polyomavirus currently known to cause human cancer. MCPyV is believed to be an etiological factor in at least 80% of cases of the rare but aggressive skin malignancy Merkel cell carcinoma (MCC). In these MCPyV+ MCC tumors, clonal integration of the viral genome results in the continued expression of two viral proteins: the viral small T antigen (ST) and a truncated form of the viral large T antigen. The oncogenic potential of MCPyV and the functional properties of the viral T antigens that contribute to neoplasia are becoming increasingly well-characterized with the recent development of model systems that recapitulate the biology of MCPyV+ MCC. In this review, we summarize our understanding of MCPyV and its role in MCC, followed by the current state of both in vitro and in vivo model systems used to study MCPyV and its contribution to carcinogenesis. We also highlight the remaining challenges within the field and the major considerations related to the ongoing development of in vitro and in vivo models of MCPyV+ MCC.

ZNS- und Nebennierenmetastasen bei Merkelzellkarzinom – ein besonderer Fall

Das Merkelzellkarzinom ist ein hochaggressiver, seltener Hauttumor. Bei Erstdiagnose bestehen bereits bei 30% der Patienten loko-regionäre Lymphknotenmetastasen. Fernmetastasen finden sich häufig in entfernten Lymphknotenstationen, der Haut, den abdominellen Organen und den Knochen. Bei Auftreten von Fernmetastasen reduziert sich das 5-Jahres-Überleben auf 18%. Wir berichten über eine Patientin mit Merkelzellkarzinom, die ein Jahr nach Erstdiagnose Fernmetastasen im ZNS und den Nebennieren entwickelte. Beide Lokalisationen sind bisher selten beschrieben. Therapeutisch kamen Radiatio, Radiochirurgie und eine Immuntherapie mit Avelumab zum Einsatz. Während sich hierunter eine komplette Remission der Hirnfiliae zeigte, führte ein rasanter Progress der Nebennierenmetastasen zur Umstellung auf eine palliative platinbasierte Chemotherapie.

Stem Cells as Target for Prostate cancer Therapy: Opportunities and Challenges

Cancer stem cells (CSCs) and cells in a cancer stem cell-like (CSCL) state have proven to be responsible for tumor initiation, growth, and relapse in Prostate Cancer (PCa) and other cancers; therefore, new strategies are being developed to target such cellular populations. TLR3 activation-based immunotherapy using Polyinosinic:Polycytidylic acid (PIC) has been proposed to be used as a concomitant strategy to first-line treatment. This strategy is based on the induction of apoptosis and an inflammatory response in tumor cells. In combination with retinoids like 9cRA, this treatment can induce CSCs differentiation and apoptosis. A limitation in the use of this combination is the common decreased expression of TLR3 and its main positive regulator p53. observed in many patients suffering of different cancer types such as PCa. Importantly, human exposure to certain toxicants, such as iAs, not only has proven to enrich CSCs population in an in vitro model of human epithelial prostate cells, but additionally, it can also lead to a decreased p53, TLR3 and RA receptor (RARβ), expression/activation and thus hinder this treatment efficacy. Therefore, here we point out the relevance of evaluating the TLR3 and P53 status in PCa patients before starting an immunotherapy based on the use of PIC +9cRA to determine whether they will be responsive to treatment. Additionally, the use of strategies to overcome the lower TLR3, RARβ or p53 expression in PCa patients, like the inclusion of drugs that increase p53 expression, is encouraged, to potentiate the use of PIC+RA based immunotherapy in these patients.

Milademetan is a highly potent MDM2 inhibitor in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine carcinoma of the skin with 2 etiologies. Merkel cell polyomavirus (MCPyV) integration is present in about 80% of all MCC. Virus-positive MCC (MCCP) tumors have few somatic mutations and usually express WT p53 (TP53). By contrast, virus-negative MCC (MCCN) tumors present with a high tumor mutational burden and predominantly UV mutational signature. MCCN tumors typically contain mutated TP53. MCCP tumors express 2 viral proteins: MCPyV small T antigen and a truncated form of large T antigen. MCPyV ST specifically activates expression of MDM2, an E3 ubiquitin ligase of p53, to inhibit p53-mediated tumor suppression. In this study, we assessed the efficacy of milademetan, a potent, selective, and orally available MDM2 inhibitor in several MCC models. Milademetan reduced cell viability of WT p53 MCC cell lines and triggered a rapid and sustained p53 response. Milademetan showed a dose-dependent inhibition of tumor growth in MKL-1 xenograft and patient-derived xenograft models. Here, along with preclinical data for the efficacy of milademetan in WT p53 MCC tumors, we report several in vitro and in vivo models useful for future MCC studies.

CK20/CK7 Double Negative Merkel Cell Carcinoma In-Situ: A Case Report

An 83-year-old male with a history of both melanoma and non-melanoma skin cancers presented with a light pink non-ulcerated slightly raised 0.6 x 0.5 cm papule on his left lower extremity. Biopsy revealed a proliferation of intraepidermal round blue cells. On immunohistochemical staining, CD56, chromogranin, and pancytokeratin were faintly positive within the lesional population, while synaptophysin was strongly positive. CD45, CK5/6, CK7, CK20, Melan-A, SOX10, and TTF-1 stains were negative. There was no dermal component identified. A Merkel cell polyomavirus (MCPyV) stain was negative. Distant metastases and other in situ pathologies were excluded and a diagnosis of Merkel cell carcinoma in situ (MMCIS) was made. The majority of MCCIS lesions reported in the literature have been discovered amongst other non-melanoma neoplasms. Our findings of a MCCIS with purely intraepidermal involvements without the association with another squamous cell neoplasm is a rare finding. This article is protected by copyright. All rights reserved.

Diagnosis and treatment of Merkel cell carcinoma: European consensus-based interdisciplinary guideline - Update 2022

Merkel cell carcinoma (MCC) is a rare skin cancer, accounting for less than 1% of all cutaneous malignancies. It is found predominantly in white populations and risk factors include advanced age, ultraviolet exposure, male sex, immunosuppression, such as AIDS/HIV infection, haematological malignancies or solid organ transplantation, and Merkel cell polyomavirus infection. MCC is an aggressive tumour with 26% of cases presenting lymph node involvement at diagnosis and 8% with distant metastases. Five-year overall survival rates range between 48% and 63%. Two subsets of MCC have been characterised with distinct molecular pathogenetic pathways: ultraviolet-induced MCC versus virus-positive MCC, which carries a better prognosis. In both subtypes, there are alterations in the retinoblastoma protein and p53 gene structure and function. MCC typically manifests as a red nodule or plaque with fast growth, most commonly on sun exposed areas. Histopathology (small-cell neuroendocrine appearance) and immunohistochemistry (CK20 positivity and TTF-1 negativity) confirm the diagnosis. The current staging systems are the American Joint Committee on Cancer/Union for international Cancer control 8th edition. Baseline whole body imaging is encouraged to rule out regional and distant metastasis. For localised MCC, first-line treatment is surgical excision with postoperative margin assessment followed by adjuvant radiation therapy (RT). Sentinel lymph node biopsy is recommended in all patients with MCC without clinically detectable lymph nodes or distant metastasis. Adjuvant RT alone, eventually combined with complete lymph nodes dissection is proposed in case of micrometastatic nodal involvement. In case of macroscopic nodal involvement, the standard of care is complete lymph nodes dissection potentially followed by post-operative RT. Immunotherapy with anti-PD-(L)1 antibodies should be offered as first-line systemic treatment in advanced MCC. Chemotherapy can be used when patients fail to respond or are intolerant for anti-PD-(L)1 immunotherapy or clinical trials.

The Role of Histone Post-Translational Modifications in Merkel Cell Carcinoma

Merkel Cell Carcinoma (MCC) is a rare but highly aggressive form of non–melanoma skin cancer whose 5-year survival rate is 63%. Merkel cell polyomavirus (MCPyV), a small DNA tumor virus, is the etiological agent of MCC. Although representing a small proportion of MCC cases, MCPyV-negative MCCs have also been identified. The role of epigenetic mechanisms, including histone post-translational modifications (PTMs) in MCC, have been only partially determined. This review aims to describe the most recent progress on PTMs and their regulative factors in the context of MCC onset/development, providing an overview of current findings on both MCC subtypes. An outline of current knowledge on the potential employment of PTMs and related factors as diagnostic and prognostic markers, as well as novel treatment strategies targeting the reversibility of PTMs for MCC therapy is provided. Recent research shows that PTMs are emerging as important epigenetic players involved in MCC onset/development, and therefore may show a potential clinical significance. Deeper and integrated knowledge of currently known PTM dysregulations is of paramount importance in order to understand the molecular basis of MCC and improve the diagnosis, prognosis, and therapeutic options for this deadly tumor.

Malignant biliary obstruction due to metastatic non-hepato-pancreato-biliary cancer

Malignant biliary obstruction generally results from primary malignancies of the pancreatic head, bile duct, gallbladder, liver, and ampulla of Vater. Metastatic lesions from other primaries to these organs or nearby lymph nodes are rarer causes of biliary obstruction. The most common primaries include renal cancer, lung cancer, gastric cancer, colorectal cancer, breast cancer, lymphoma, and melanoma. They may be difficult to differentiate from primary hepato-pancreato-biliary cancer based on imaging studies, or even on biopsy. There is also no consensus on the optimal method of treatment, including the feasibility and effectiveness of endoscopic intervention or surgery. A thorough review of the literature on pancreato-biliary metastases and malignant biliary obstruction due to metastatic non-hepato-pancreato-biliary cancer is presented. The diagnostic modality and clinical characteristics may differ significantly depending on the type of primary cancer. Different primaries also cause malignant biliary obstruction in different ways, including direct invasion, pancreatic or biliary metastasis, hilar lymph node metastasis, liver metastasis, and peritoneal carcinomatosis. Metastasectomy may hold promise for some types of pancreato-biliary metastases. This review aims to elucidate the current knowledge in this area, which has received sparse attention in the past. The aging population, advances in diagnostic imaging, and improved treatment options may lead to an increase in these rare occurrences going forward.

Merkel cell carcinoma brain metastasis with radiological findings mimicking primary CNS lymphoma: illustrative case

BACKGROUND

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine tumor with a high likelihood of distant metastasis. Approximately 30 cases of MCC brain metastasis have been reported. The authors report a case of MCC brain metastasis with imaging findings mimicking primary central nervous system lymphoma.

OBSERVATIONS

A 69-year-old asymptomatic White female with a past medical history of rheumatoid arthritis and MCC of the right cheek with no known regional or distant spread presented with a right frontal lobe lesion discovered incidentally on a surveillance scan. Brain magnetic resonance imaging revealed a vividly enhancing homogeneous lesion with restricted diffusion on diffusion-weighted imaging and corresponding apparent diffusion coefficient maps. Imaging characteristics suggested a highly cellular mass consistent with primary central nervous system lymphoma; however, given the likelihood of metastasis, resection was recommended. An intraoperative frozen section suggested lymphoma. However, further examination revealed positive cytokeratin 20 staining for a tumor, and a final diagnosis of MCC brain metastasis was made.

LESSONS

Imaging characteristics of MCC brain metastasis can vary widely. A high level of suspicion should be maintained in a patient with a known history of MCC. Aggressive resection is recommended, regardless of appearance on scans or pathology of frozen sections, because MCC can mimic other intracranial pathologies.

Scientific and clinical developments in Merkel cell carcinoma: A polyomavirus-driven, often-lethal skin cancer

Merkel cell carcinoma (MCC) is a primary neuroendocrine skin cancer that recurs in ~40% of cases. Merkel cell polyomavirus (MCPyV) and ultraviolet (UV)-induced mutations are two major causative factors of MCC. Virus-positive MCCs express polyomavirus oncoproteins that are highly immunogenic yet are required for ongoing tumor growth. Virus-negative MCCs have a high burden of UV-DNA mutations that encode tumor-specific UV-neoantigens. Thus, both UV- and virus-induced MCCs are highly immunogenic, enabling diverse T-cell targeted therapies. Optimal MCC management is challenging given its rarity, aggressive nature, rapidly evolving care guidelines, and fundamental differences in management compared to other skin cancers. MCC is often managed aggressively with extensive surgery, radiotherapy or systemic therapy, frequently leading to toxicities that might have been avoidable while still achieving optimal disease control. Thus, multi-disciplinary care is crucial for providing patients with the best possible outcomes. The outlook for many patients with advanced MCC has progressed remarkably over the past decade due to PD-1 pathway blocking agents that provide durable benefit for a substantial subset of MCC patients. The management of early-stage MCC has also improved due to better approaches to integrate surgery and radiotherapy. Prognostic accuracy and ongoing surveillance have advanced due to stage-specific recurrence data and sophisticated "liquid biopsies" that allow early detection of disease recurrence. Here we summarize both recent striking progress and pressing challenges such as PD-(L)1-refractory MCC, and management of MCC patients with immune dysfunction. We also highlight diverse resources to allow providers to take advantage of recent progress in this fast-moving field.

Merkel Cell Carcinoma: An updated review of pathogenesis, diagnosis, and treatment options

Merkel cell carcinoma is a rare neuroendocrine carcinoma that typically appears in sun-exposed areas of the elderly. It has a poor prognosis and with its incidence projected to increase, it is vital for dermatologists to remain up to date with recent updates in this malignancy's pathogenesis and treatment. In the past few decades Merkel cell carcinoma's pathogenesis, more specifically its relation to the Merkel cell polyomavirus, has sparked further interest in the study of this carcinoma. Most cases are attributed to malignant transformation secondary to the Merkel cell polyomavirus, with a minority derived from DNA damage resulting from ultraviolet radiation. Investigators have also determined that there are immunologic influences in the development and prognosis of Merkel cell carcinoma, as individuals with HIV, solid organ transplants, and lymphoproliferative malignancies are at a greater risk of developing this carcinoma. Also, this immunologic link carries treatment value, as immunologic therapies are currently being investigated. This article provides a comprehensive review of the epidemiology and pathogenesis of Merkel cell carcinoma as well as the current treatments available and clinical trials underway. We also touch upon the updated National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology in respect to its diagnosis and recommended treatment modalities.

Epigenetic Dysregulations in Merkel Cell Polyomavirus-Driven Merkel Cell Carcinoma

Merkel cell polyomavirus (MCPyV) is a small DNA virus with oncogenic potential. MCPyV is the causative agent of Merkel Cell Carcinoma (MCC), a rare but aggressive tumor of the skin. The role of epigenetic mechanisms, such as histone posttranslational modifications (HPTMs), DNA methylation, and microRNA (miRNA) regulation on MCPyV-driven MCC has recently been highlighted. In this review, we aim to describe and discuss the latest insights into HPTMs, DNA methylation, and miRNA regulation, as well as their regulative factors in the context of MCPyV-driven MCC, to provide an overview of current findings on how MCPyV is involved in the dysregulation of these epigenetic processes. The current state of the art is also described as far as potentially using epigenetic dysregulations and related factors as diagnostic and prognostic tools is concerned, in addition to targets for MCPyV-driven MCC therapy. Growing evidence suggests that the dysregulation of HPTMs, DNA methylation, and miRNA pathways plays a role in MCPyV-driven MCC etiopathogenesis, which, therefore, may potentially be clinically significant for this deadly tumor. A deeper understanding of these mechanisms and related factors may improve diagnosis, prognosis, and therapy for MCPyV-driven MCC.

18F-FDG PET/CT for post-treatment surveillance imaging of patients with stage III Merkel cell carcinoma

To investigate diagnostic and prognostic value of ¹⁸F-FDG PET/CT for surveillance imaging in patients treated for Stage III Merkel cell carcinoma (MCC). Methods: This retrospective study included 61 consecutive stage III MCC patients, who were clinically asymptomatic and underwent surveillance FDG-PET/CT. Findings were correlated with either pathology and/or clinical/imaging follow-up. Median follow-up period was 4.8 years. Statistical analyses were performed. Results: FDG-PET/CT detected unsuspected recurrences in 33% patients (20/61) with lesion-based sensitivity, specificity, and accuracy of 92%, 93%, and 93%, respectively. Mean±SD SUV for malignant and benign lesions was 7.5±3.9 and 3.8±2.0, respectively. Unknown distant metastases, as first recurrence site, were noted in 12 of 61 patients. Those with positive disease on FDG-PET/CT within one year of definitive treatment had relatively worse overall survival (p<0.0001). After adjustment on stage, risk of death increased with higher SUV_max (HR for one unit=1.17;P = 0.006) and with a higher number of positive lesions on FDG-PET/CT (HR for one additional lesion = 1.60;p<0.001). Conclusion: Post-definitive treatment surveillance FDG-PET/CT scan detects unsuspected recurrences and has prognostic value. Inclusion of FDG-PET/CT within the first 6 months after definitive treatment would be appropriate for surveillance and early detection of recurrence. Our data merits further studies to evaluate the prognostic implications.

Abdominal metastases from Merkel cell carcinoma: Prevalence and presentation on CT examination in 111 patients

PURPOSE

The purpose of this study was to report the prevalence and imaging features of abdominal metastases from Merkel cell carcinoma (MCC) on computed tomography (CT) examinations.

MATERIALS AND METHODS

A total of 111 patients with MCC from two institutions were initially identified. Of these, 27 patients (27/111; 24.3%) had abdominal metastases from MCC present on CT examination. There were 19 men and 8 women with a mean age of 75  ± 10.8 (SD) years (age range: 46-92 years). CT examinations were retrospectively reviewed by two radiologists and analyzed quantitatively for the number and dimensions of abdominal metastases from MCC and qualitatively in terms of location, margins, contours, homogeneity, patterns of enhancement, vascular involvement and extension of metastases from MCC.

RESULTS

Fifteen patients (15/27; 56%) had abdominal metastatic disease at initial diagnosis and twelve (12/27; 44%) developed abdominal metastases during the course of the disease. The mean number of locations of abdominal metastases was 2.1 ± 1.12 (SD) (range: 1-5). Abdominal metastases involved abdominal lymph nodes (16/27; 59%), adrenal glands/kidneys/retroperitoneum (14/27; 52%), mesentery/peritoneum (13/27; 48%), liver (7/27; 26%) and pancreas (7/27; 26%). Vascular involvement was found in association with peritoneal/mesenteric metastases in 6/13 (46%) patients with intraperitoneal metastases or in association with abdominal lymph nodes in 4/16 (25%) patients. Ureteral encasement and/or dilatation was found in 4/14 (28%) patients with retroperitoneal metastases and 3/16 (19%) patients with abdominal lymph nodes. Metastases to the liver, pancreas, peritoneum, retroperitoneum and adrenal glands displayed internal enhancement during the arterial phase in 1/2 (50%), 4/5 (80%), 4/7 (57%) and 5/8 (62%) patients for whom arterial phase was available, respectively.

CONCLUSION

Metastases from MCC have a prevalence of 24.3% on CT examination and may involve a variety of abdominal organs, mainly lymph nodes, peritoneal and retroperitoneal structures, but also the liver and pancreas. CT features of abdominal metastases from MCC include hypervascularity during the arterial phase of enhancement and eventually vascular and ureteral involvement.

Merkel Cell Carcinoma With Isolated Pancreatic Metastasis

Merkel cell carcinoma (MCC) is a highly aggressive cutaneous neuroendocrine carcinoma, frequently associated with distant metastasis. However, recurrence of MCC manifesting with only pancreatic involvement is exceedingly rare. A 53-year-old man presented to our institution with abdominal discomfort 3 months after initial resection of chest wall MCC. Imaging revealed lesions in the pancreas and peripancreatic lymph nodes. Pathology obtained through endoscopic ultrasound confirmed recurrence of MCC. He underwent chemotherapy with cisplatin and etoposide, resulting in a complete resolution of the pancreatic lesions. Unfortunately, he passed away from sudden cardiac arrest while being in remission from MCC. Immunohistochemistry is crucial in differentiating MCC from primary pancreatic glandular and neuroendocrine tumors. While there are no definitive guidelines in the management of pancreatic lesions associated with MCC, checkpoint inhibitor immunotherapy is increasingly being used.

The Human Bone Marrow Is Host to the DNAs of Several Viruses

The long-term impact of viruses residing in the human bone marrow (BM) remains unexplored. However, chronic inflammatory processes driven by single or multiple viruses could significantly alter hematopoiesis and immune function. We performed a systematic analysis of the DNAs of 38 viruses in the BM. We detected, by quantitative PCRs and next-generation sequencing, viral DNA in 88.9% of the samples, up to five viruses in one individual. Included were, among others, several herpesviruses, hepatitis B virus, Merkel cell polyomavirus and, unprecedentedly, human papillomavirus 31. Given the reactivation and/or oncogenic potential of these viruses, their repercussion on hematopoietic and malignant disorders calls for careful examination. Furthermore, the implications of persistent infections on the engraftment, regenerative capacity, and outcomes of bone marrow transplantation deserve in-depth evaluation.

Clinical benefit of baseline imaging in Merkel cell carcinoma: Analysis of 584 patients

BACKGROUND

Merkel cell carcinoma (MCC) guidelines derive from melanoma and do not recommend baseline cross-sectional imaging for most patients. However, MCC is more likely to have metastasized at diagnosis than melanoma.

OBJECTIVE

To determine how often baseline imaging identifies clinically occult MCC in patients with newly diagnosed disease with and without palpable nodal involvement.

METHODS

Analysis of 584 patients with MCC with a cutaneous primary tumor, baseline imaging, no evident distant metastases, and sufficient staging data.

RESULTS

Among 492 patients with clinically uninvolved regional nodes, 13.2% had disease upstaged by imaging (8.9% in regional nodes, 4.3% in distant sites). Among 92 patients with clinically involved regional nodes, 10.8% had disease upstaged to distant metastatic disease. Large (>4 cm) and small (<1 cm) primary tumors were both frequently upstaged (29.4% and 7.8%, respectively). Patients who underwent positron emission tomography-computed tomography more often had disease upstaged (16.8% of 352), than those with computed tomography alone (6.9% of 231; P = .0006).

LIMITATIONS

This was a retrospective study.

CONCLUSIONS

In patients with clinically node-negative disease, baseline imaging showed occult metastatic MCC at a higher rate than reported for melanoma (13.2% vs <1%). Although imaging is already recommended for patients with clinically node-positive MCC, these data suggest that baseline imaging is also indicated for patients with clinically node-negative MCC because upstaging is frequent and markedly alters management and prognosis.

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.

Molecular Pathogenesis of Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine carcinoma of the skin with two distinct etiologies. Clonal integration of Merkel cell polyomavirus DNA into the tumor genome with persistent expression of viral T antigens causes at least 60% of all MCC. UV damage leading to highly mutated genomes causes a nonviral form of MCC. Despite these distinct etiologies, both forms of MCC are similar in presentation, prognosis, and response to therapy. At least three oncogenic transcriptional programs feature prominently in both forms of MCC driven by the virus or by mutation. Both forms of MCC have a high proliferative growth rate with increased levels of cell cycle-dependent genes due to inactivation of the tumor suppressors RB and p53, a strong MYC signature due to MYCL activation by the virus or gene amplification, and an attenuated neuroendocrine differentiation program driven by the ATOH1 transcription factor.

Merkel Cell Carcinoma of the Hand in a Young Patient

Merkle cell carcinoma (MCC) is a rare, malignant neuroendocrine skin cancer that typically affects patients in the seventh decade of life. Reports of MCC affecting young patients are limited, and there are few mentions of the management of these lesions when they present on the hand and fingers. Hand surgeons must be educated regarding the diagnosis of MCC and the multidisciplinary management required to achieve optimal results. We present the case of a 22-year-old woman with MCC arising on the dorsum of the second digit. Treatment with wide local excision, coverage of the resulting soft tissue defect with a reverse second dorsal metacarpal artery flap, and subsequent radiotherapy resulted in no evidence of disease recurrence or metastasis at 1 year. This case highlights the commonly encountered delay in the diagnosis of this lesion and the necessity for a high index of suspicion when evaluating a patient with an enlarging, solitary hand nodule.

Metastatic Merkel Cell Carcinoma Masquerading as Multiple Immune-Related Adverse Events

Merkel cell carcinoma is a rare cutaneous neuroendocrine carcinoma with a high rate of regional and distant metastasis and mortality. Here, we report a novel case of Merkel cell carcinoma which presented as a primary lesion to the left cheek with regional lymph node involvement and was treated with pembrolizumab and radiation. Widely metastatic disease eventually revealed on autopsy clinically mimicked immune-related organ insult leading to management with immunosuppressants. The patient also had a biopsy-confirmed immune-related cutaneous adverse event during admission. The case highlights a rare circumstance in which disease progression masqueraded as multiple immune-related end-organ adverse events. Contribution of on-target anti-PD-1 toxicity remains a possibility.

Patterns of Metastasis in Merkel Cell Carcinoma

Background

Merkel cell carcinoma (MCC) is a cutaneous neuroendocrine malignancy with a propensity for regional and distant spread. Because of the relative infrequency of this disease, the patterns of metastasis in MCC are understudied.

Methods

Patients with American Joint Committee on Cancer (8th edition) stage I–IV MCC treated at our institution were identified (1/1/2008–2/28/2018). The first site of metastasis was classified as regional [regional lymph node (LN) basin, in-transit] or distant. Distant metastasis-free (DMFS) and MCC-specific (MSS) survival were estimated.

Results

Of 133 patients, 64 (48%) had stage I, 13 (10%) stage II, 48 (36%) stage III, and 8 (6%) stage IV disease at presentation. The median follow-up time in patients who remained alive was 36 (interquartile range 20–66) months. Regional or distant metastases developed in 78 (59%) patients. The first site was regional in 87%, including 73% with isolated LN involvement, and distant in 13%. Thirty-seven (28%) patients eventually developed distant disease, which most commonly involved the abdominal viscera (51%) and distant LNs (46%) first. The lung (0%) and brain (3%) were rarely the first distant sites. Stage III MCC at presentation was significantly associated with worse DMFS (hazard ratio 4.87, P = 0.001) and stage IV disease with worse MSS (hazard ratio 6.30, P = 0.002).

Conclusions

Regional LN metastasis is the most common first metastatic event in MCC, confirming the importance of nodal evaluation. Distant disease spread appears to have a predilection for certain sites. Understanding these patterns could help to guide surveillance strategies.

Patterns of distant metastases in 215 Merkel cell carcinoma patients: Implications for prognosis and surveillance

Approximately one‐third of Merkel cell carcinoma (MCC) patients eventually develop distant metastatic disease. Little is known about whether the location of the primary lesion is predictive of initial distant metastatic site, or if survival likelihood differs depending on the metastatic site. Such data could inform imaging/surveillance practices and improve prognostic accuracy. Multivariate and competing‐risk analyses were performed on a cohort of 215 MCC patients with distant metastases, 31% of whom had two or more initial sites of distant metastasis. At time of initial distant metastasis in the 215 patients, metastatic sites (n = 305) included non‐regional lymph nodes (present in 41% of patients), skin/body wall (25%), liver (23%), bone (21%), pancreas (8%), lung (7%), and brain (5%). Among the 194 patients who presented with MCC limited to local or regional sites (stage I‐III) but who ultimately developed distant metastases, distant progression occurred in 49% by 1 year and in 80% by 2 years following initial diagnosis. Primary MCC locations differed in how likely they were to metastasize to specific organs/sites (P < .001). For example, liver metastases were far more likely from a head/neck primary (43% of 58 patients) versus a lower limb primary (5% of 39 patients; P < .0001). Skin‐only distant metastasis was associated with lower MCC‐specific mortality as compared to metastases in multiple organs/sites (HR 2.7; P = .003), in the liver (HR 2.1; P = .05), or in distant lymph nodes (HR 2.0; P = .045). These data reflect outcomes before PD1‐pathway inhibitor availability, which may positively impact survival. In conclusion, primary MCC location is associated with a pattern of distant spread, which may assist in optimizing surveillance. Because it is linked to survival, the site of initial distant metastasis should be considered when assessing prognosis.