Background/Objectives: Tumor-immune system interactions shape the progression of cutaneous squamous cell carcinoma (cSCC). Serum biomarkers for risk stratification remain limited. Complement factor H (CFH) regulates the alternative complement pathway. It has been linked to immunosuppression and cSCC development in tissue-based studies. We investigated whether serum CFH is associated with tumor aggressiveness and may help predict immunotherapy outcomes in advanced cSCC. Methods: In this retrospective, single-center study, pre-treatment serum CFH levels were measured in 104 cSCC patients (62 high-risk and 42 advanced) using ELISA. Associations with clinical characteristics, disease stage, and response to cemiplimab were analyzed. Subgroup comparisons considered immune status and inflammatory comorbidities. Results: Advanced cSCC patients had significantly higher CFH levels than high-risk patients (OR 0.13, p = 0.026), independent of tumor diameter or invasion depth. Among advanced cSCC cases, lower baseline CFH was associated with more prolonged progression-free survival (median 19.8 vs. 3.07 months, p = 0.029; HR 0.29, p = 0.014), independent of covariates including immunosuppression. CFH levels during therapy did not predict treatment response. ROC analysis showed moderate discriminatory ability with CFH alone (AUC 0.625), which improved when combined with clinical variables in a multivariable risk model (AUC 0.767). Conclusions: Serum CFH is an independent predictor of cemiplimab response and reflects biological aggressiveness in cSCC beyond conventional high-risk features. These findings support the use of CFH in clinical risk models and warrant external validation in multicenter cohorts.

Cutaneous squamous cell carcinoma (cSCC) is the second most frequent skin cancer. In locally advanced and metastatic cases, the PD-1 inhibitor cemiplimab has transformed treatment, with response rates around 50 %. Despite its success, predictive biomarkers remain an unmet clinical need. D-dimer levels have been associated with poor outcomes in various cancers but have not been studied in cSCC. To assess the potential of serum D-dimer levels as predictive and monitoring biomarkers for disease control in advanced cSCC patients receiving cemiplimab. In this retrospective monocentric study, 45 advanced cSCC patients treated with cemiplimab were analyzed. D-dimer levels before and during treatment were correlated with clinical disease control data. Clinical characteristics, including cardiovascular disease and anticoagulatory medication, were monitored and mapped among groups. Elevated baseline D-dimer levels were significantly associated with reduced time to progression (TTP; HR 3.46, p = 0.007). Multivariable logistic regression showed that high baseline D-dimers independently predicted lower disease control rate (DCR; OR 0.13, p = 0.011) and overall response rate (ORR; OR 0.06, p = 0.0182). After treatment start, D-dimer levels did not significantly correlate with response metrics. High pre-treatment D-dimer levels are an independent predictive biomarker for reduced DCR and ORR in advanced cSCC patients treated with cemiplimab. On-treatment D-dimer levels did not exhibit discriminatory value as a monitoring biomarker in this real-world cohort. Further studies are needed to confirm the role of D-dimer levels in response prediction in advanced cSCC.

Background: Immune checkpoint inhibition (ICI) is the standard treatment for advanced melanoma patients. Despite its high efficacy compared to previous treatment options, immune-related adverse events (irAEs) occur frequently. While most of the patients experience mild to moderate irAEs, some patients develop severe to lethal irAEs under ICI treatment; hence, biomarkers are urgently required. Methods: In this retrospective single-center study, 157 advanced melanoma patients treated with ICI at the University Medical Center Hamburg–Eppendorf were included. IrAEs were correlated with clinico-pathological parameters, disease-related outcomes, and irAE-free survival. Results: In our cohort, 130 out of 157 patients receiving immunotherapy experienced irAE, of which more than half experienced irAE Grade ≥ 3. The most common irAE independent of its grade included cutaneous irAE, colitis, endocrine irAE, and hepatitis. Patients experiencing irAE had significantly longer progression-free survival (PFS) and overall survival (OS) compared to patients who did not experience irAE under ICI therapy. Stratification by irAE groups revealed that musculoskeletal irAEs are associated with the longest, whereas myocarditis is associated with the shortest OS and PFS. IrAE was a significant beneficial prognosticator for PFS in univariate, but not in multivariate Cox regression analysis. With respect to OS, the occurrence of irAE was an independent prognostic factor among ECOG status ≥ 2 and uveal melanoma. ROC analysis demonstrated that D-dimers have moderate predictive capability for irAE occurrence. Cox regression analysis demonstrated that elevated D-dimers and PD-1 monotherapy vs. CTLA-4 and PD-1 combination regimen are the only independent prospective prognostic markers for irAE-free survival. Conclusions: Our study demonstrates that different irAE across the irAE spectrum have a different impact on the PFS and OS of advanced melanoma patients. D-dimers may be used as a blood-based biomarker for irAE prediction, warranting future validation in multi-center studies.

Despite substantial clinical benefit from immune checkpoint inhibitors (ICI), advanced melanoma remains challenging due to frequent treatment resistance. Resistance may be intrinsic (primary) or emerge over time (secondary). Biomarkers predicting distinct resistance phenotypes before therapy are lacking. As key mediators of cellular communication, extracellular vesicles (EVs) represent promising biomarkers. This study aimed to identify baseline EV proteome–derived pathways and biomarkers associated with overall, primary, and secondary resistance to ICI in advanced melanoma and to derive biomarker signatures predictive of progression‐free survival (PFS). EVs were isolated from pretreatment plasma samples of 46 patients with advanced melanoma using size exclusion chromatography and ultracentrifugation. Proteomic profiling was performed by liquid chromatography–mass spectrometry using DIA‐NN. Pathway enrichment and network analyses were conducted using Reactome, Metascape, Cytoscape, and DAVID. Resistance‐associated proteins were integrated into composite biomarker signatures and evaluated for association with PFS. Overall resistance was characterized by enrichment of platelet‐ and complement‐associated pathways. Primary resistance was associated with enhanced Fc gamma receptor (FCGR) signaling and downregulation of KSRP‐associated post‐transcriptional regulatory processes. In contrast, secondary resistance was preceded by distinct baseline EV proteomic patterns involving complement activation and reduced hemostasis‐ and platelet‐related pathways. EV‐derived biomarker signatures for overall, primary, and secondary resistance independently discriminated patients according to PFS. Baseline plasma EV proteomics reveals distinct systemic biological programs associated with different resistance phenotypes to ICI in advanced melanoma. EV‐derived biomarker signatures enable stratification by PFS and warrant validation in larger, multicentric cohorts.

Targeted therapies (TT) improve outcomes in BRAF-mutant melanoma. Pre-clinical data suggest that anticoagulation (AC) and platelet aggregation inhibition (PAI) may have antitumoral effects. We evaluated the impact of concomitant AC or PAI on outcomes in patients receiving TT. We analyzed 1296 patients with unresectable stage III-IV BRAF-mutant melanoma treated with BRAF plus MEK inhibitors (2016-2024) in the prospective multicenter ADOReg registry. Patients were categorized as receiving no antithrombotic therapy (ATT; n = 1125), PAI (n = 73; acetylsalicylic acid or clopidogrel), or AC (n = 98; direct oral anticoagulants, low-molecular-weight heparin, or vitamin K antagonists). Median follow-up was 1.3 years. Compared with patients without ATT, those receiving AC had significantly improved 12-month progression-free survival (PFS; HR 0.55, 95 % CI 0.39-0.78, p = 0.001) and overall survival (OS; HR 0.35, 95 % CI 0.19-0.64, p = 0.001). Direct oral anticoagulants showed the most pronounced PFS benefit (HR 0.40, 95 % CI 0.25-0.64, p < 0.001). PAI was not associated with a significant difference in PFS, but multivariable Cox regression indicated a reduced hazard of death (HR 0.48, 95 % CI 0.27-0.87, p = 0.015). Concomitant AC, particularly factor Xa-inhibiting direct oral anticoagulants, was associated with improved survival in melanoma patients undergoing TT. These findings support prospective trials evaluating AC as concomitant therapy in advanced melanoma.

Immune checkpoint inhibitors (ICIs) frequently cause thyroid immune‐related adverse events (irAEs). Permanent hypothyroidism, the clinically most relevant phenotype, requires lifelong hormone replacement. We investigated its incidence, course, risk factors, and prognostic relevance under pembrolizumab. This retrospective single‐center study included patients from the Departments of Gynecology and Dermatology who received ≥ 3 cycles of pembrolizumab between 2018 and 2024. Permanent hypothyroidism occurred in 30/188 patients (16.0%). Thyrotoxicosis was observed in 46/188 (24.5%) and de novo hypothyroidism in 33/188 (17.6%). Overt thyrotoxicosis progressed to permanent hypothyroidism in 71% of cases. Nearly all permanent cases were overt at first detection (29/30), and most patients were asymptomatic. Permanent hypothyroidism developed earlier than transient courses (median 15 vs. 26 weeks), and no new permanent events occurred beyond 50 weeks. Prior chemotherapy was strongly associated with permanent hypothyroidism (33% vs. 11%; p = 0.001), whereas age, sex, tumor stage, treatment setting, and other systemic therapies were not. Permanent hypothyroidism was not associated with progression‐free survival, recurrence‐free survival, or overall survival. Permanent hypothyroidism is a common pembrolizumab‐related irAE, typically occurring within the first 6 months but occasionally up to 12 months after treatment initiation. Prior chemotherapy emerged as an independent predictor of permanent hypothyroidism. Most cases were mild and manageable with oral levothyroxine. These findings suggest that cycle‐based thyroid monitoring may warrant continuation through the first 12 months of ICI therapy, with heightened attention to patients with prior chemotherapy exposure.