Multicentre, Interventional Prospective Study to Evaluate the Efficiency of Pre- and Postoperative Margin Determination of Basal Cell Carcinomas Using Optical Coherence Tomography and Line-field Confocal Optical Coherence Tomography During Micrographically Controlled Surgery

Basal cell carcinoma (BCC) is the most common type of skin cancer worldwide and occurs predominantly in fair-skinned populations. In Germany, approximately one in three individuals will develop BCC during their lifetime. Although BCC rarely metastasizes, it shows locally destructive growth with irregular, finger-like extensions into surrounding tissue, which can make complete surgical removal challenging. The majority of tumors arise in the sun-exposed head and neck region.

Micrographic surgery (Mohs micrographic surgery, MMS) represents the gold standard treatment for high-risk BCC, as it allows complete margin control and offers the highest cure rates. However, MMS is often time-consuming and resource-intensive because multiple sequential excision stages may be required until histopathology confirms complete tumor removal (R0 resection). Preoperative estimation of tumor margins is usually based on clinical examination and dermoscopy with a standard safety margin of 2-3 mm. This approach may be inaccurate, particularly in tumors with subclinical extension, which can lead either to unnecessarily large excisions or to residual tumor tissue requiring additional surgical stages.

Non-invasive imaging techniques have increasingly been investigated to improve the preoperative assessment of BCC margins. Optical coherence tomography (OCT) and the more recently developed line-field confocal optical coherence tomography (LC-OCT) allow high-resolution, real-time imaging of the skin. These technologies enable visualization of skin structures with near-histological resolution and can detect characteristic morphological features of BCC in vivo. Previous studies have demonstrated good diagnostic accuracy of OCT and LC-OCT for the detection and subtyping of BCC and suggest that these methods may also be useful for defining tumor margins before surgery.

In particular, LC-OCT combines the advantages of conventional OCT with the cellular resolution of confocal microscopy, allowing both vertical and horizontal imaging of the skin at high resolution. This enables detailed visualization of tumor architecture and potentially facilitates the detection of subclinical tumor extensions beyond the clinically visible borders.

The present multicenter randomized controlled study aims to evaluate whether LC-OCT-guided preoperative margin assessment can improve the efficiency of MMS. In the intervention group, the lateral tumor margins are examined preoperatively using LC-OCT. If tumor structures are detected at the planned resection margin, the surgical margin is extended accordingly before the first excision step. MMS is then performed according to the standard surgical protocol with histopathological examination of the margins. In centers where available, excised tissue may additionally be examined postoperatively using ex vivo LC-OCT or confocal microscopy to correlate imaging findings with histopathology.