Risk of melanoma and nonmelanoma skin cancer with immunosuppressants, part I: Calcineurin inhibitors, thiopurines, IMDH inhibitors, mTOR inhibitors, and corticosteroids

Immunosuppression is a well-documented risk factor for skin cancer, as exemplified by the 65- to 250-fold higher squamous cell carcinoma risk, 10-fold higher basal cell carcinoma risk, and 0 to 8-fold higher melanoma risk in solid organ transplant recipients (SOTRs) receiving potent, prolonged courses of immunosuppressive therapies. Numerous immune system components have been shown to either suppress or promote tumor growth, and immunosuppressive drugs may have additional effects on proliferative pathways independent of the immune system. Thus, evaluation of the specific regimen by the dermatologist is key for assessing skin cancer risk in each patient. In the present manuscript, the immune-mediated mechanisms of skin cancer development and regression are first reviewed. Next, a synthesis of the evidence shows the differing effects of immunosuppressive agents commonly used in SOTRs on melanoma and nonmelanoma skin cancer risk. These include systemic calcineurin inhibitors, thiopurines, IMDH (inosine monophosphate dehydrogenase) inhibitors, mTOR (mammalian target of rapamycin) inhibitors, and systemic corticosteroids. Finally, recommendations for skin cancer screening in SOTRs are discussed. We further offer recommendations for select nontransplant patients who may benefit from routine skin cancer screening due to risks associated with specific immunosuppressant exposure, and we propose evidence-based strategies for minimizing high-risk immunosuppressant use in clinical practice.