Clinical Review

Emerging Noninvasive Treatments of Nonmelanoma Skin Cancers

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References

Aminolevulinic Acid Hydrochloride
Aminolevulinic acid hydrochloride is a red light PS used to treat AKs since 2011 and BCCs since 2017 in Europe in addition to AKs in the United States since 2016.38,39 A phase 3 noninferiority clinical trial in Europe of 281 patients compared the treatment of nonaggressive BCCs with ALA to methyl aminolevulinate (MAL) cream.40 The study found a complete response rate of 93.4% vs 91.8%. Superficial BCCs treated with ALA had a clearance rate of 94.7% vs 96.4% with MAL, while nodular BCCs treated with ALA had a clearance rate of 85.7% vs 76.2% with MAL. A 1-year clinical follow-up showed similar recurrence rates (8.4% for ALA vs 8.5% for MAL).40 The results of this study led to an expanded indication in Europe to include the treatment of BCCs.38 Aminolevulinic acid hydrochloride currently is undergoing phase 3 clinical trials in the United States for approval for the treatment of superficial BCCs (NCT03573401). If similar outcomes are achieved, US patients may have access to an alternative nonsurgical treatment of BCCs. The ongoing US trial is exclusively investigating the efficacy and safety for superficial BCCs, which may limit FDA approval to only superficial BCCs, accounting for only 8.4% to 24.1% of all BCCs.35,41,42

Laser Therapy

Ablative and nonablative lasers have been used to treat NMSCs in the literature. Ablative lasers destroy tumors through vaporization of tissue water, whereas nonablative lasers target the vasculature of tumors while preserving the surrounding tissue.43,44 Nonablative lasers include pulsed dye lasers (PDL) and Nd:YAG lasers. Examples of ablative lasers include CO2 and erbium:YAG lasers. Given the status of lasers as an emerging treatment method, there currently is no standardized laser setting for any of the laser therapies used to treat NMSCs. Although there is the potential for optimal cosmetic outcomes and a limited side-effect profile for nonablative laser therapies, there are limited data on long-term follow-up to study recurrence rates and establish a more standardized treatment protocol.

Pulsed Dye Lasers
Although there were no studies on PDL therapy alone in 2018, a study published in 2019 evaluated a combination laser treatment using a 595-nm PDL and 1927-nm fractional laser for the treatment of 93 BCCs, yielding a 95.7% (89/93) clearance rate and 4.5% (4/89) recurrence rate over a follow-up period of up to 6 years (range, 2.53 months to 6.03 years).45 Studies of PDL prior to 2018 had follow-ups ranging from 2 weeks to 6 months.46-51 Although the majority were biopsy-proven BCCs, reflectance confocal microscopy also was used for same-day diagnoses. Long-term follow-up included clinical examinations, dermoscopy, and optical coherence tomography.45 The clearance rate (95.7%) using noninvasive imaging in conjunction with the combination laser treatment was superior to both histologic and clinical clearance rates of prior PDL-only studies, which ranged from 25% to 95%.46-51 To have long-term follow-up data, the study used noninvasive imaging with clinical follow-up because histology would not be viable for long-term follow-up. This study was retrospective rather than prospective, which was a limitation.45

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Nd:YAG Lasers
The majority of studies utilizing Nd:YAG lasers investigated their efficacy in treating BCCs, with the exception of 1 study of facial SCCs. This major study in 2009 of 627 BCCs showed a 2.5% recurrence rate after a follow-up time of 3 months to 5 years.52 Nd:YAG lasers continue to be investigated, including a more recent study of 31 extrafacial, biopsy-proven BCCs that were treated with the 1064-nm Nd:YAG laser, which showed a 90% histologic clearance on 1-month follow-up after a single treatment.53 In 2019, a retrospective review of 16 BCC lesions on the head, neck, trunk, and extremities showed 100% clearance after 1 treatment, with an average follow-up period of 9 months (range, 6–15 months).54 In a retrospective review, Markowitz and Psomadakis55 contributed data supporting the further investigation and use of the 1064-nm Nd:YAG laser for BCC treatment while leveraging noninvasive imaging to demonstrate a same-day management model. Seventeen BCC lesions on the face and body were diagnosed by reflectance confocal microscopy and treated with an Nd:YAG laser, and clearance was monitored clinically, dermoscopically, and by optical coherence tomography. There was 100% clearance of the lesions in the study, with 82.4% (14/17) clearing after 1 treatment; mean follow-up was 103 days (range, 48–371 days).55 These studies were limited by their short follow-up time; long-term data are needed to determine true rates of recurrence.

Ablative Lasers
Ablative lasers also have been used in the treatment of NMSCs. In addition to the potentially increased healing time compared to nonablative lasers, other limitations of ablative laser therapy include residual tumor burden or recurrence that may not be easily visualized in scarred tissue after nonablative management.44

Conclusion

Although MMS remains the gold standard for invasive management of NMSCs, studies from 2018 and beyond (eTable) expanded not only on MMS topics such as increased patient access and improved techniques but also on the increasing potential of noninvasive treatments. Some of the noninvasive therapies were entirely new compounds, whereas others were already in use for a different disease indication. Furthering our knowledge and expanding our repertoire of management options will prepare us as the number of patients affected by NMSCs increases.

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