For the 1.8 million annual US cases of cutaneous squamous cell carcinoma (CSCC), the standard staging systems—AJCC and Brigham and Women's—leave a blind spot: they miss roughly 20% of patients who will ultimately develop metastasis. SkylineDx, a Rotterdam-based molecular diagnostics company, aims to fill that gap with a new gene expression signature. At the 22nd EADO Congress, the company presented data showing its test outperforms both staging systems in identifying high-risk patients, potentially changing who receives adjuvant therapy.
The signature, derived from primary tumor tissue, stratifies patients into risk groups for metastasis. In a validation cohort, the test reclassified a significant portion of patients deemed low-risk by staging as high-risk, and vice versa. This mirrors SkylineDx's earlier success in melanoma with its Merlin test, which helped guide sentinel lymph node biopsy decisions. The CSCC signature is still in development, but the data suggests a clear path to clinical utility.
For investors, the key question is reimbursement. SkylineDx's Merlin test for melanoma is covered by Medicare, but CSCC diagnostics face a more fragmented payer landscape. The company has not disclosed pricing or a timeline for a commercial launch. However, if the signature can reduce unnecessary surgeries or guide adjuvant immunotherapy—like cemiplimab (Libtayo) or pembrolizumab (Keytruda)—it could capture a significant share of the CSCC diagnostic market, estimated at over $500 million annually.
Competitors like Castle Biosciences (DecisionDx-SCC) and Veracyte (now part of Exact Sciences) already offer gene expression tests for CSCC. SkylineDx's differentiation lies in its focus on metastasis risk specifically, rather than recurrence. The EADO data positions SkylineDx as a potential challenger, but the company will need to deliver a larger validation study and secure guideline inclusion to gain traction.
If this signature can reliably identify the 5% of CSCC patients who metastasize, it could save thousands from overtreatment and redirect resources to those who truly need it.
Looking ahead, SkylineDx plans to present additional data at upcoming oncology meetings and is exploring partnerships for commercial distribution. The CSCC diagnostic market is heating up, and SkylineDx's new data gives it a credible entry point.
