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.

Anti-tumor effects of tirbanibulin in squamous cell carcinoma cells are mediated via disruption of tubulin-polymerization.

Topical tirbanibulin is a highly effective and well tolerated novel treatment option for actinic keratoses (AKs). This study aimed to characterize the mode of action of tirbanibulin in keratinocytes (NHEK) and cutaneous squamous cell carcinoma (cSCC) cell lines (A431, SCC-12) in vitro. Tirbanibulin significantly reduced proliferation in a dose-dependent manner in all investigated cell lines, inhibited migration, and induced G2/M-cell cycle arrest only in the cSCC cell lines analyzed, and induced apoptosis solely in A431, which showed the highest sensitivity to tirbanibulin. In general, we detected low basal expression of phosphorylated SRC in all cell lines analyzed, therefore, interference with SRC signaling does not appear to be the driving force regarding the observed effects of tirbanibulin. The most prominent tirbanibulin-mediated effect was on ß-tubulin-polymerization, which was especially impaired in A431. Additionally, tirbanibulin induced an increase of the proinflammatory cytokines IL-1α, bFGF and VEGF in A431. In conclusion, tirbanibulin mediated anti-tumor effects predominantly in A431, while healthy keratinocytes and more dedifferentiated SCC-12 were less influenced. These effects of tirbanibulin are most likely mediated via dysregulation of ß-tubulin-polymerization and may be supported by proinflammatory aspects.

Reinduction of Hedgehog Inhibitors after Checkpoint Inhibition in Advanced Basal Cell Carcinoma: A Series of 12 Patients.

For patients with advanced basal cell carcinoma (aBCC) first-line treatment with hedgehog inhibitors (HHIs) and second-line treatment with PD1 inhibitors (PD1i) is available, offering combination and sequencing options. Here, we focus on the efficacy and safety of HHI reinduction after PD1i failure. Retrospective data analysis was performed with 12 patients with aBCC (locally advanced (n = 8)/metastatic (n = 4)). These patients (male:female 6:6, median age 68 years) initially received HHIs, leading to complete/partial response (66%) or stable disease (33%). Median treatment duration was 20.8 (2-64.5) months until discontinuation due to progression (n = 8), adverse events (n = 3), or patient request (n = 1). Subsequent PD1 inhibition (pembrolizumab 42%, cemiplimab 58%) yielded a partial response (8%), stable disease (33%), or progression (59%). Median treatment duration was 4.1 (0.8-16.3) months until discontinuation due to progression (n = 9), adverse events (n = 1), patient request (n = 1), or missing drug approval (n = 1). HHI reinduction resulted in complete/partial response (33%), stable disease (50%), or progression (17%). Median treatment duration was 3.6 (1-29) months. Response duration in the four responding patients was 2-29+ months. Thus, a subgroup of patients with aBCC responded to reinduction of HHI following PD1i failure. Therefore, this sequential treatment represents a feasible treatment option.