Merkel Cell Carcinoma: Evaluation of the Clinico-Pathological Characteristics, Treatment Strategies and Prognostic Factors in a Monocentric Retrospective Series (n=143)

Croix B, Gao L. m276-SL-PBD eradicates tumors and instigates long-lasting tumor-free survival in Merkel cell carcinoma preclinical models

Merkel cell carcinoma (MCC) is a rare but aggressive neuroendocrine carcinoma, and immune checkpoint inhibitors (ICIs) are the only approved therapy; nonetheless, resistance is notable and there is a critical need for novel effective therapies. Recently, CD276 was identified as a promising therapeutic target in human cancers. In preclinical studies, a modified CD276 antibody-drug conjugate (ADC) with pyrrolobenzodiazepine (m276-SL-PBD) elicited more potent anti-tumor effects than two CD276 ADCs currently in clinical trials. Here, we uncover notable CD276 expression in MCC patient tumors, and demonstrate m276-SL-PBD efficacy against MCC preclinical models. Complete eradication is observed in all xenografts bearing CD276 expression, with 82% achieving 180-day tumor-free survival after 4 or 5 weekly doses, and m276-SL-PBD remained efficacious against relapsed tumors. Of clinical relevance, m276-SL-PBD retains its potency in MCC-bearing humanized mice. Importantly, no detectable adverse effects were observed. Thus, m276-SL-PBD is a promising therapy for patients unsuitable or resistant to ICIs.

Sentinel Lymph Node Biopsy: Is There a Role in Non-Melanoma Skin Cancer? A Systematic Review

BACKGROUND/OBJECTIVES

Sentinel Lymph Node Biopsy (SLNB) aims at identifying clinically occult nodal metastases. It is the standard staging procedure for patients with T1b to T4 primary cutaneous melanoma. Moreover, it is recommended whenever the risk of a positive SLNB is >5%, according to the National Comprehensive Cancer Network Melanoma guidelines. When considering Non-Melanoma Skin Cancer (NMSC), the SLNB could play a role in tumors that mainly spreads via lymphatics, but strong evidence is missing. In this paper, the hot topics and controversies are reviewed; Methods: A PRISMA systematic review was carried out on the PubMed (MEDLINE) library from 2004-2024, searching for studies on SLNB in NMSC; Results: Seventy articles and 6379 patients undergoing SLNB for Squamous Cell Carcinoma (SCC), Merkel Cell Carcinoma (MCC), and Porocarcinoma were included. Overall, the SLNB positivity rate in these NMSCs was 24.4%, with an SNLB detection rate of 97.6%. Specifically, the SLNB positivity rate was 12.3% for high-risk cutaneous SCC, 24.4% for anogenital SCC, 29.3% for MCC, and 30.6% for Porocarcinoma. Most papers concluded that SLNB is safe, feasible, and significant in these malignancies; Conclusions: SLNB should be discussed and offered to every patient with MCC, and it should be discussed and considered in "high risk" SCC and Porocarcinoma for staging and prognostic purposes, aiming to identify a subgroup of patients who may benefit the most from early treatments.

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.

TRK Protein Expression in Merkel Cell Carcinoma Is Not Caused by NTRK Fusions

Merkel cell carcinoma (MCC) is a rare and aggressive cutaneous malignant tumor with neuroendocrine differentiation, with a rapidly growing incidence rate, high risk of recurrence, and aggressive behavior. The available therapeutic options for advanced disease are limited and there is a pressing need for new treatments. Tumors harboring fusions involving one of the neurotrophin receptor tyrosine kinase (NTRK) genes are now actionable with targeted inhibitors. NTRK-fused genes have been identified in neuroendocrine tumors of other sites; thus, a series of 76 MCCs were firstly analyzed with pan-TRK immunohistochemistry and the positive ones with real-time RT-PCR, RNA-based NGS, and FISH to detect the eventual underlying gene fusion. Despite 34 MCCs showing pan-TRK expression, NTRK fusions were not found in any cases. As in other tumors with neural differentiation, TRK expression seems to be physiological and not caused by gene fusions.

Short-Interval, Low-Dose Peptide Receptor Radionuclide Therapy in Combination with PD-1 Checkpoint Immunotherapy Induces Remission in Immunocompromised Patients with Metastatic Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a neuroendocrine skin cancer of the elderly, with high metastatic potential and poor prognosis. In particular, the primary resistance to immune checkpoint inhibitors (ICI) in metastatic (m)MCC patients represents a challenge not yet met by any efficient treatment modality. Herein, we describe a novel therapeutic concept with short-interval, low-dose ¹⁷⁷Lutetium (Lu)-high affinity (HA)-DOTATATE [¹⁷⁷Lu]Lu-HA-DOTATATE peptide receptor radionuclide therapy (SILD-PRRT) in combination with PD-1 ICI to induce remission in patients with ICI-resistant mMCC. We report on the initial refractory response of two immunocompromised mMCC patients to the PD-L1 inhibitor avelumab. After confirming the expression of somatostatin receptors (SSTR) on tumor cells by [⁶⁸Ga]Ga-HA-DOTATATE-PET/CT (PET/CT), we employed low-dose PRRT (up to six treatments, mean activity 3.5 GBq per cycle) at 3–6 weeks intervals in combination with the PD-1 inhibitor pembrolizumab to restore responsiveness to ICI. This combination enabled the synergistic application of PD-1 checkpoint immunotherapy with low-dose PRRT at more frequent intervals, and was very well tolerated by both patients. PET/CTs demonstrated remarkable responses at all metastatic sites (lymph nodes, distant skin, and bones), which were maintained for 3.6 and 4.8 months, respectively. Both patients eventually succumbed with progressive disease after 7.7 and 8 months, respectively, from the start of treatment with SILD-PRRT and pembrolizumab. We demonstrate that SILD-PRRT in combination with pembrolizumab is safe and well-tolerated, even in elderly, immunocompromised mMCC patients. The restoration of clinical responses in ICI-refractory patients as proposed here could potentially be used not only for patients with mMCC, but many other cancer types currently treated with PD-1/PD-L1 inhibitors.

Development of metastatic Merkel cell carcinoma following the excision of same‐sided recurrent auricular melanoma

Merkel cell carcinoma (MCC) is a rare neuroendocrine malignancy of the skin that is highly aggressive and often metastasizes early. MCC is diagnosed based on histopathological findings and is most commonly treated with surgical resection, which may be accompanied by chemotherapy and/or radiation. This report describes a 55‐year‐old male patient with the history of recurrent malignant melanoma of the right pinna and subsequent excision. Three years following the excision of melanoma, he presented with a lesion to the right forehead as well as a right‐sided neck mass that were found to be metastatic Merkel cell carcinoma.

Hemato-Oncological Diseases as Risk Factor for Recurrence or Metastasis of Pleomorphic Dermal Sarcoma

Background

Atypical fibroxanthoma (AFX) and pleomorphic dermal sarcoma (PDS) are increasingly common sarcomas of the skin with a genetic UV signature. Immunosuppression is a known risk factor for developing other UV-induced skin cancers such as cutaneous squamous cell carcinoma (cSCC), basal cell carcinoma (BCC), and Merkel cell carcinoma with increased mortality. In case reports or small case series of AFX/PDS patients, immunosuppression has been hypothesized as a risk factor for the development of distant metastases. The aim of the present study was to analyze immunosuppression as a risk factor for AFX/PDS in a large patient cohort.

Methods

A cohort of 164 patients with AFX/PDS (47 AFX and 117 PDS) was collected between 2003 and 2021 and analyzed for clinicopathological data with a special focus on immunosuppression.

Results

Of all patients, 29.9% had any kind of immunosuppression; 6.4% of the AFX and 12.0% of the PDS patients had underlying hemato-oncological diseases. Patients with immunosuppression due to an underlying hemato-oncological disease had a significantly increased risk of progressing to (p = 0.010) and developing distant organ metastases (p = 0.000).

Conclusions

Immunosuppression seems to be a risk factor for developing AFX/PDS with worse clinical outcomes. Therefore, immunosuppression, especially underlying hemato-oncological diseases, should be considered in the treatment and follow-up care of patients with AFX/PDS.