Initial Experience in Using Optical Coherence Tomography in Defining Radiation Fields for Head and Neck Basal Cell Carcinoma

Definitive Radiotherapy (RT) brings tissue conservation. Skin cancer RT area delineation can be a challenge especially in basal cell carcinoma (BCC) with morpheaform features. We report our initial experience of 11 consecutive patients imaged with Optical Coherence Tomography (OCT) prior to treatment. The gross tumour volume (GTV) was marked by a radiation oncologist (RO) using a strong light only. OCT was then done by a dermatologist blinded to the RO markings. The difference in areas, if any, were computed and tabulated. Relevant outcomes were recorded. Of the 11 patients there were nine females and two males. Average age was 65 (47–87) years. Patients had initially a total of 13 lesions between them. Of the initial 13 lesions, seven were lesions without previous treatment, five were recurrent post-surgery, one post-cryotherapy. The most common site was the nose (8/13), then lips (2/13). Eyelid, scalp and temple had one each. There were a mix of BCC histologies; infiltrating (4/13), nodular (5/13) morpheaform (3/13) and one was unclassified. The initial RO GTV area on average was 584 (50–<styled-content style-type="number">2400</styled-content>) mm², the average OCT area was 420 (63–<styled-content style-type="number">2350</styled-content>) mm². OCT decreased the size of the GTV with an average change of 164 (-<styled-content style-type="number">1650</styled-content> to + 760) mm², that is, 28%. The assistance of OCT was not limited to morpheaform lesions. OCT also found three more BCCs, and one lesion thought clinically to be BCC was not. OCT avoided a geographic miss. Three (3/11) were treated with other modalities; two with Moh’s surgery, one with Rhenium-188. Eight patients with ten lesions were treated with definitive RT. RT was planned using the OCT area as the correct area. All had clinical complete response (CR) at post-RT follow up. In the five patients having OCT following RT, all had a continuing complete response at an average of 6.8 months post-RT.