Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy, and their use in combination with radiation therapy (RT) has become increasingly utilized to optimize positive outcomes. The cutaneous adverse reactions from RT as well as ICIs are both well documented; however, in combination these cutaneous toxicities can be exacerbated. ICIs and RT may work synergistically to create an enhanced immune response against the tumor cells. This synergistic effect has been reported to occur both locally at the site of RT, as well as systemically via an abscopal effect. Fortunately, this combination of treatment does not increase the incidence of cutaneous reactions, although several cases have reported enhanced skin toxicity at the site of RT. RT is thought to create an ‘immunocompromised skin district’ or localized immune dysregulation in irradiated skin. This review summarizes previously published case reports and discusses the cutaneous adverse reactions from ICI and RT combination therapy. Properly identifying ICI and RT induced skin reactions depends on several factors including patient history, sequence of therapies, timing of reaction, and histological findings. Skin reactions from combination therapy can range in severity and include ICI-induced radiation recall dermatitis, as well as uncommon presentations of Stevens-Johnson syndrome, lichen planus, and bullous pemphigoid which are localized to or enhanced within areas of prior radiation exposure. It is important for oncologists and dermatologists alike to be aware of the spectrum of reactions associated with ICI and RT.
Radiation recall pneumonitis induced by PD-1/PD-L1 blockades: mechanisms and therapeutic implications
