D-TECT is a prospective, multicenter, non-interventional observational study investigating whether pretreatment D-dimer levels predict disease control in patients with locally advanced or metastatic cutaneous squamous cell carcinoma treated with cemiplimab in routine clinical care.

D-dimers are routinely available laboratory markers related to activation of the coagulation system. Previous single-center data suggest that elevated pretreatment D-dimer levels may be associated with poorer disease control under cemiplimab. In D-TECT, a single pretreatment D-dimer value and prospectively collected routine clinical follow-up data will be analyzed to validate this association in a multicenter real-world setting. No study-specific treatment decisions, imaging procedures, or additional blood draws are mandated by the study.

Cutaneous squamous cell carcinoma (cSCC) is one of the most common skin cancers. While most cases can be treated with curative local therapy, a subgroup of patients develops locally advanced or metastatic disease requiring systemic treatment. Cemiplimab, a PD-1 inhibitor, is an established systemic treatment option for advanced cSCC. However, validated routine biomarkers predicting disease control under cemiplimab are lacking.

D-dimers are fibrin degradation products and sensitive markers of coagulation activation. In a prior single-center retrospective analysis, elevated pretreatment D-dimer levels were associated with lower disease control, lower objective response, and shorter progression-free survival in patients with advanced cSCC treated with cemiplimab. D-TECT is designed to prospectively validate this observation in a multicenter real-world cohort.

Eligible patients are adults with histologically confirmed locally advanced or metastatic cSCC for whom cemiplimab treatment is planned as part of routine clinical care. A D-dimer measurement is documented within 7 days before the first cemiplimab dose up to the day of first administration before infusion. Subsequent clinical data, including tumor response, progression, survival, treatment discontinuation, and thromboembolic events, are collected from routine medical records during follow-up.

The primary endpoint is disease control within the first 6 months after initiation of cemiplimab. The primary confirmatory analysis compares disease control between patients with high versus low pretreatment D-dimer values using the prespecified cutoff of 0.91 mg/L FEU derived from the prior single-center study. If the primary analysis is statistically significant, the same primary endpoint will be tested hierarchically using the local laboratory-defined upper limit of normal. Additional analyses include objective response rate, progression-free survival, overall survival, thromboembolic events, diagnostic performance measures of the predefined cutoffs, sensitivity analyses, and exploratory analyses addressing inter-site assay heterogeneity.

Inclusion Criteria:

• Histologically confirmed locally advanced or metastatic cutaneous squamous cell carcinoma
• Planned initiation of systemic treatment with cemiplimab as part of routine clinical care
• Pretreatment D-dimer measurement performed within 7 days before initiation of cemiplimab treatment up to the day of first administration before infusion
• Age 18 years or older at the time of consent
• ECOG performance status 0 to 2
• Written informed consent for study participation and pseudonymized collection and analysis of clinical and laboratory data

Exclusion Criteria:

• Prior treatment with immune checkpoint inhibitors in curative or palliative intent for cutaneous squamous cell carcinoma
• Concurrent second malignancy requiring systemic treatment, such as chemotherapy, immunotherapy, or targeted therapy
• Clinically unstable comorbidity, including NYHA class III-IV heart failure or active systemic infection
• Acute symptomatic thrombosis or pulmonary embolism within 4 weeks before the pretreatment D-dimer measurement
• Incidental asymptomatic thromboembolic events detected during clinical diagnostic work-up or following an elevated D-dimer result are not exclusion criteria and will be documented
• Physician-estimated life expectancy of less than 3 months or severe non-tumor-related comorbidity likely to preclude assessment of the clinical course within the first 6 months
• Lack of capacity to consent or legal guardianship without valid legal representation

Adult patients with histologically confirmed locally advanced or metastatic cutaneous squamous cell carcinoma for whom systemic treatment with cemiplimab is planned as part of routine clinical care at participating oncology/dermato-oncology centers.

No individual participant data will be shared. Study data will be analyzed in pseudonymized form by the coordinating study center. Any further use of study data beyond the present research question would require additional ethical and data protection review and, where applicable, additional consent.