Applications of Lasers in Medical Dermatology

A relatively recent development in the use of lasers has been LLLT, which refers to the use of lasers below levels where they would cause any thermal effects, thereby limiting tissue damage. Although the technology has existed for decades, there has been a recent flurry of reports extolling the many benefits of LLLT; however, the true physiologic effects of LLLT have yet to be determined, with many studies trying to elucidate its numerous effects on various signaling pathways, cell proliferation, and cellular respiration.^23-26 Upon reviewing the literature, the list of cutaneous conditions that are being treated with LLLT is vast, spanning acne, vitiligo, wounds, burns, psoriasis, and alopecia, among others.¹⁵ It is important to consider that the definition of LLLT in the literature is rather broad with a wide range of wavelengths, fluences, and power densities. As such, the specific laser settings and protocols may vary considerably among different practitioners and therefore the treatment results also may vary. Nevertheless, many studies have hinted at promising results in the use of LLLT in conditions that may have previously been extremely difficult to treat (eg, alopecia). Earlier trials had demonstrated a faster resolution time in patients with alopecia areata when LLLT was added to a topical regimen²⁷; however, the improvement was modest and lesions tended to improve with or without LLLT. Perhaps more compelling is the use of LLLT in treating androgenetic alopecia, a condition for which a satisfying facile treatment would truly carry great impact. Although physicians should be cautious of studies regarding LLLT and hair regrowth that are conducted by groups who may stand to benefit from producing such a device, the results are nonetheless notable, if only for the relative paucity of other therapeutic approaches toward this condition.^28,29 A randomized, double-blind, controlled, multicenter trial showed significant improvements in median hair thickness and density with LLLT (P=.01 and P=.003, respectively), though global appearance did not change significantly.³⁰

Laser Treatment of Skin Cancer

Lasers also have been used to treat cutaneous malignancies. Although they may be powerful in the treatment of these conditions, this treatment approach must be used with caution. As with any superficial treatment modality for skin cancer, it is difficult to ascertain if a lesion has been completely treated without any residual cancer cells, and therein lies the main caveat of laser treatment. With the use of a modality that causes a cutaneous response that may mask any underlying process, it is important to ensure that there is a reasonable degree of certainty that this treatment can effectively remove a cancerous lesion in its entirety while avoiding the theoretical risk that disturbing underlying vasculature and/or lymphatics may be modulating the ability of a cancer to metastasize. Thankfully, current evidence does not suggest that there are any downsides to laser treatment for malignancies. Clinically, we know that basal cell carcinomas (BCCs) often feature prominent vasculature, with telangiectases being used as a clinical marker to suggest the diagnosis of a BCC. Capitalizing on this aspect of the clinical lesion, PDL has been used to treat BCCs in 2 small studies with a response rate of approximately 75% for small BCCs in both studies.^31,32 A recent randomized controlled trial showed significant superiority of PDL as compared to the control (P<.0001) in treatment of BCC, with nearly 80% (44/56) of cases showing histologically proven complete remission at 6-month follow-up.³³ Thus, we have some promising data that suggest PDL may be a viable treatment option in BCC, especially in areas that are difficult to treat surgically.

Additionally, a newer treatment approach for BCC capitalizes on the ability of confocal microscopy to provide a feasible, bedside imaging modality to identify tumor margins. Confocal microscopy has been used as a road map to identify where and how to apply the laser treatment, thus allowing for a higher likelihood of complete destruction of the tumor, at least in theory.³⁴ Although the concept of using confocal microscopy to guide laser treatment of skin cancer has been shown in smaller proof-of-concept case series, it remains to be seen if it is not only an efficacious approach that may be widely adopted but also whether it is pragmatic to do so, as the equipment and expertise involved in using confocal microscopy is not trivial.

Finally, lasers also have been used in the treatment of mycosis fungoides (MF), or cutaneous T-cell lymphoma. It has been suggested that this modality is an excellent treatment option as a skin-directed therapy for stage IA or IB MFs limited to the acral surfaces or MF palmaris et plantaris.³⁵ The reasoning behind this approach was the effectiveness of narrowband UVB for early-stage MF, with an excimer laser operating at a similar wavelength (308 nm) and offering similar therapeutic benefits while limiting adverse effects to surrounding skin.³⁶ More recently, the excimer laser was applied to a small population of 6 patients, with 3 achieving complete response, 1 with partial response, 1 with stable disease, and 1 with progressive disease. The authors were careful to point out that the excimer laser should not be thought of as a replacement for narrowband UVB in early-stage MF but rather as an adjunctive treatment of specific targeted lesional areas.³⁶