Immune checkpoint inhibitor associated lichenoid eruptions: a review of non-steroidal systemic maintenance therapies.

Immune checkpoint inhibitors (ICIs) have transformed the landscape of cancer therapy. As the number of malignancy indications for ICIs continues to increase, so does the incidence of cutaneous immune-related adverse events (cirAEs), which occur in up to 71.5% of patients on immunotherapy. Lichenoid eruptions (LEs), characterized by mucocutaneous lesions mimicking lichen planus, are one of the most common cirAEs, occurring in up to 17% of patients receiving immunotherapy. There are currently no standardized guidelines for the management of LEs. While oral corticosteroids are effective in improving lichenoid eruptions and are often needed short-term for higher-grade toxicities, they decrease immunotherapy efficacy by blunting the anti-tumor response. Thus, it is imperative to recognize alternative systemic therapies that may be used for long-term maintenance treatment of LEs without negatively impacting ICI treatment efficacy. In this review, we summarize the current evidence regarding the efficacy of non-steroidal systemic therapies used to treat ICI-induced LEs, including classic LEs, as well as two subtypes-hypertrophic and oral disease-as these are often causes of ICI treatment interruption. Low-dose methotrexate and systemic retinoids are the most frequently used non-steroidal medications to treat ICI-induced LEs and have the strongest efficacy data to support their use. Promising emerging therapeutics include dupilumab, hydroxychloroquine, apremilast, and interleukin (IL)-17 inhibitors. While anti-inflammatory antibiotics have also been used to treat ICI-induced LEs, antibiotics should generally be avoided as they can alter the gut microbiome, which can lead to decreased ICI efficacy and an increased risk of colitis. Further controlled and systematic clinical studies are warranted to refine treatment approaches to ICI-induced LEs.