Optical coherence tomography for diagnosing recurrent or residual basal cell carcinoma after topical treatment: A diagnostic cohort study

Background: Recurrent/residual basal cell carcinoma (BCC) after topical treatment may not be visible during clinical and dermatoscopic examination (CDE). Optical coherence tomography (OCT) may detect these subclinical recurrences or residues. Objective: To compare the diagnostic accuracy of CDE with that of CDE combined with OCT (CDE-OCT) for detecting recurrent/residual BCC after topical treatment of superficial BCC. Methods: In this diagnostic cohort study, the suspicion level for recurrence or residue was recorded on a 5-point confidence scale. All patients with high suspicion of recurrence or residue based on CDE and/or CDE-OCT were referred for punch biopsy. Patients with a low suspicion on CDE and CDE-OCT were asked to (voluntarily) undergo a control biopsy. Histopathologic results of the biopsy were used for verification of CDE and CDE-OCT diagnoses (gold standard). Results: This study included 100 patients. A histopathologic recurrent/residual BCC was found in 20 patients. For recurrence or residue detection, sensitivity was 100% (20 of 20) for CDE-OCT and 60% (12 of 20) for CDE (P =.005) and specificity was 95% for CDE-OCT and 96.3% for CDE (P =.317). The area under the curve for CDE-OCT (0.98) was significantly higher than that for CDE (0.77) (P =.001). Limitations: Results are based on 2 OCT assessors. Conclusion: Compared with CDE alone, CDE-OCT results in a significantly higher ability to detect recurrent/residual BCCs after topical treatment.