This diagnostic cohort study will include patients (18+ years) who underwent a biopsy and D-OCT scan for lesions suspect for BCC skin cancer. Patient data was retrieved from a pre-existing registry (METC: 2022-3555). All D-OCT scans were obtained at the outpatient dermatology clinic of Maastricht University Medical Center+ (MUMC+) using a Vivosight Multi-beam Swept-Source Frequency Domain OCT scanner (Michelson Diagnostics Maidstone, Kent, UK; resolution <7.5 µm lateral, <5 µm axial; depth of focus 1.0 mm; scan area 6 × 6 mm). All scanned lesions were histopathologically examined by a dermatopathologist blinded to D-OCT scans and D-OCT assessment.

Vivosight Multi-beam Swept-Source Frequency Domain OCT scanner (Michelson Diagnostics Maidstone, Kent, UK; resolution <7.5 µm lateral, <5 µm axial; depth of focus 1.0 mm; scan area 6 × 6 mm).

We will evaluate the ability of OCT assessors to discriminate BCC from non-BCC using OCT without and with dynamic functionality. The diagnostic certainty for BCC detection will be expressed on a five-point confidence scale. A high confidence score (confidence score=4) is considered a positive OCT test results. In these cases, biopsy could effectively be omitted. Lower confidence scores (confidence score≤3) are considered negative OCT test results as in these cases, biopsy remains necessary for a definitive or alternative diagnosis. The primary outcome of interest is the sensitivity of a high confidence BCC diagnosis because we want to evaluate whether the dynamic functionality increases the proportion of correctly classified BCCs.

We will evaluate the ability of OCT assessors to discriminate each individual BCC subtype from the other two subtypes using OCT without and with dynamic functionality. Cases that resulted in a high confidence diagnosis (confidence score=4) will be included in the analyses. Three analyses will be performed to calculate the sensitivity to detect sBCC, nBCC or iBCC and the specificity to identify non-sBCC, non-nBCC or non-iBCC subtypes using histopathology as reference test. In this respect, sensitivity is defined as the proportion of a specific BCC subtype, that is correctly classified as such by the OCT assessor (i.e. sBCC, nBCC or iBCC), whereas specificity is defined as the proportion of the other two subtypes that is correctly classified as such (i.e sBCC/nBCC, sBCC/iBCC or nBCC/iBCC). The primary outcome of interest is the sensitivity. We want to evaluate whether the dynamic functionality increases the proportion of correctly classified subtypes .