Skin cancer is the most common malignancy worldwide, and non-melanoma skin cancers (NMSC) in particular, including basal cell carcinomas (BCC) and squamous cell carcinomas, constitute around 80 percent of all skin cancers. It is estimated that approximately 3.5 million new cases of NMSC occur every year in the U.S., exceeding that of all other cancers combined. Despite the high prevalence of NMSC, they can be effectively treated and cured with low recurrence when detected at an early stage. BCCs are known to be slow growing and rarely metastasize to other parts of the body; however, if left untreated, they can cause extensive local tissue invasion and destruction.
The US Preventive Services Task Force recently has updated their recommendations for routine full-body skin checks for skin cancer screening and concluded there is insufficient evidence for routine screening in those without pre-existing risk factors (such as a personal history of skin cancer, or a first-degree family member with history of malignant melanoma) (JAMA 2016:316:429-35). Currently, the argument calling for the necessity of skin cancer screening has been supported by the use of dermoscopy and, therefore, a potential need exists for new technology that will reduce the costs of skin cancer prevention. The emergence of novel imaging devices in both the research and clinical settings will address this growing demand and allow for advancements in diagnostic and minimally invasive dermatology.
Noninvasive Imaging in Dermatology
Over the past decade, noninvasive imaging technologies, including optical coherence tomography (OCT) and reflectance confocal microscopy (RCM), have been used in cutting-edge research and clinical settings to assist in the diagnosis and treatment of a variety of skin conditions. These devices provide the advantage of real-time, in vivo imaging of concerning lesions without having to proceed directly to a tissue biopsy. While these technologies have not yet replaced the role of the biopsy, which is still considered to be the gold standard in diagnosing many concerning lesions, they can still enhance overall quality of care.
Three factors used in assessing the quality of novel imaging devices in dermatology include field-of-view (FOV), cellular clarity, and depth penetration (Exp Dermatol 2016: DOI: 10.1111/exd.13103). Typically, there exists an inverse relationship between cellular clarity and depth penetration. The highest cellular resolution is demonstrated in RCM, but the depth penetration and FOV are somewhat limited.
Despite having lower cellular clarity compared to RCM, OCT has been useful in monitoring lesions given its increased FOV and depth penetration. OCT utilizes reflected light to produce cross-sectional subcutaneous images of tissue at a higher resolution than ultrasound, with a depth penetration of 2 mm, and a spatial resolution better than 7.5 [mu]m (J Clin Aesthet Dermatol 2015; 8: 14-20, Clin Cosmet Investig Dermatol 2015;8:345-54).
Furthermore, the development of speckle-variance OCT (SV-OCT), otherwise known as dynamic OCT (D-OCT), allows for imaging of tissue vasculature, providing greater detail for discrimination of malignant lesions, as they often display discrete foci of neovascularization (Dermatology Online Journal, 22. doj_30620, J Eur Acad Dermatol Venereol 2015; doi: 10.1111/jdv.13311). While OCT has been well-established in the diagnosis of NMSC, the advent of SV-OCT brings promise to expanding the role of OCT in improving the diagnosis of malignant melanoma, one of the deadliest forms of skin cancer.
Optical Coherence Tomography
OCT produces images are similar to ultrasound technology. While the broad applicability of ultrasound imaging is due to its increased depth and FOV (Exp Dermatol 2016: DOI: 10.1111/exd.13103), certain specialties called for greater magnification of a smaller region of the body. OCT was initially used in the field of ophthalmology to produce images of the retina. Its sensitivity in image quality combined with its overall safety profile made it a highly coveted diagnostic tool for an extremely delicate structure in the body. Since then, OCT has made its way into the world of dermatology for the same beneficial qualities.
Studies and reviews in the recent literature have demonstrated the applicability of OCT in the diagnosis of non-melanocytic lesions of the skin (J Clin Aesthet Dermatol 2015; 8: 14-20, Clin Cosmet Investig Dermatol 2015;8:345-54). OCT also has been shown to be useful in defining tumor margins of non-melanoma skin cancers beyond the clinically apparent extent of tumor prior to resection. Researchers have found the diagnostic accuracy of BCCs improved from 65.8 percent on a purely clinical basis to as high as 87.4 percent with the use of OCT (Br J Dermatol 2015;173:428-35). Researchers found OCT can further refine clinically estimated borders during Mohs micrographic surgery (MMS) for BCCs and potentially reduce the area size of excised tissue. Finally, it was demonstrated that OCT can assist in accurately diagnosing a suspicious NMSC lesion, define its lateral margins, and detect residual tumor foci post-excision to ensure complete removal.
Studies collectively suggest OCT can potentially reduce the number of Mohs layers required for removal of the lesion, and thus decrease operative time while minimizing the need for future office visits that would otherwise be required for re-excision. Following an excision, OCT can continue to provide detailed monitoring of tumor recurrence. Statistically, OCT has been shown to increase the sensitivity of tumor detection, and thus decrease the rate of false positive lesions. This ultimately reduces the cost and cosmetic concerns associated with unnecessary excisions of suspicious but ultimately benign skin lesions (J Clin Aesthet Dermatol 2015; 8: 14-20, Clin Cosmet Investig Dermatol 2015;8:345-54).
OCT remains an innovative and promising noninvasive imaging device that has the potential to increase patient survival by improving diagnostic accuracy, thereby leading to earlier detection and treatment of skin cancers. The use of these safe, efficient, and user-friendly devices also will result in fewer biopsies of benign lesions, preserving normal skin and minimizing undesired cosmetic side effects. As a cutting-edge device with tremendous potential that elevates the field of dermatology, there is an increasing demand for further initiative in research and clinical applicability.
While malignant melanoma continues to be a challenge for dermatologists, new advancements within OCT may open the door for improved diagnosis of this deadly cancer. Noninvasive imaging modalities will play an important role not just in the realm of malignancy, but also in distinguishing and monitoring benign skin growths and other dermatologic conditions including psoriasis, cutaneous inflammation, and onychomycosis.
KATIE WANG, DO, is a Clinical Research Fellow in Dermatology at the Mount Sinai Hospital and SUNY Downstate Medical Center. AMANDA LEVINE, MD, is a Clinical Research Fellow in Dermatology at the Mount Sinai Hospital and SUNY Downstate Medical Center. ORIT MARKOWITZ, MD, is the Director of Pigmented Lesions and Skin Cancer and Assistant Professor at the Mount Sinai Hospital, Adjunct Professor at SUNY Downstate Medical Center, Director of Pigmented Lesions at the Brooklyn VA Hospital, and Chief of Dermatology at the Queens General Hospital.