Blistering skin side‐effects associated with checkpoint inhibitor treatment for cancer

Checkpoint inhibitors (CPIs) are new types of treatments that have been shown to be effective against several cancers by boosting a person’s immune system to ﬁght off the underlying cancer. CPIs have signiﬁcantly improved the overall survival of people diag-nosed with cancer. However, skin-related side-effects of CPIs are common (up to 49%), although more severe reactions such as blistering conditions, for example bullous pemphigoid, are rare. In this UK-based multicentre study, we wanted to ﬁnd out how many patients on CPIs developed blistering reactions, how they presented, what treatment was needed and if there were any underlying factors that might make these side-effects more likely. We reviewed data from 7,391 adults with cancers treated with CPI at four hospitals in the UK between 2006 and 2019. We found that 22 (0 (cid:1) 3%) patients had blistering side-effects. Most patients were male, with melanoma and had a median age of 76 years. Patients reported itching as a signiﬁcant symptom (91%), followed by blisters (82%), rash (45%) and wheals (23%). These side-effects commonly affected the lower limbs (41%) and mucosal surfaces (mouth/genitals) (27%). The median time to onset of side-effects was 12 months after starting the CPI, and lasted for 6 months. In two patients the side-effects occurred after the CPI treatment was completed. In most patients treatment with topical steroids was required and a signiﬁcant number of patients needed oral steroids. A few patients were treated with non-steroid-based agents. CPI was permanently stopped in 55% of the patients and temporarily stopped in 20% to manage the side-effects. We concluded that it is important to recognize the side-effects of CPIs promptly to reduce interruptions to lifesaving CPI therapy and improve patient outcomes.