Proceedings Article | 24 February 2020
KEYWORDS: Tumors, Photodynamic therapy, Skin, Photography, 3D image processing, 3D metrology, Cameras, Light sources, 3D modeling, Skin cancer
Basal cell carcinoma (BCC) is a common skin cancer caused by chronic UV exposure. Photodynamic therapy (PDT), a non-surgical, non-scarring modality, can clear superficial BCC lesions but thick (nodular) lesions are more refractory. To improve overall PDT efficacy for BCC, we are conducting a clinical trial to ascertain whether neoadjuvant treatment with Vitamin D prior to ALA-PDT (5-aminolevulinic acid and blue light) can improve the rate of tumor clearance. Study patients undergo three PDT treatments, with sessions spaced two months apart. Prior to each PDT session, patients take a Vitamin D pill or a placebo pill for up to 14 days, in a randomized double-blind fashion. To quantify tumor shrinkage after each PDT treatment, we are employing high-precision 3D photography using a LifeViz Micro camera (Quantificare, Inc). With this approach, individual tumors are rendered in 3D coordinate space and important parameters such as tumor height and volume, which could not otherwise be obtained using standard photography, are measured. Amongst 45 BCC lesions evaluated, 17 (37.8%) disappeared after the first PDT treatment, 12 (26.7%) after the second, and 7 (15.6%) after the third, for a final clinical clearance rate of 80%. For treatment-responsive lesions, decreases in absolute volume after the first, second, and third treatment were 81.4%, 66.2%, and 80.9%, respectively. Corresponding decreases in lesion surface area were 78.8%, 70.2%, and 77.6%. The similar incremental changes in lesion size after each treatment reassures us that this technique can be used to successfully determine BCC clearance rates ± Vitamin D.
