Immune checkpoint inhibitors (ICIs), often broadly referred to as immunotherapy, are being prescribed at increasing rates due to their effectiveness in treating a growing number of advanced solid tumors and hematologic malignancies.1 It has been well established that T-cell signaling mechanisms designed to combat foreign pathogens have been involved in the mitigation of tumor proliferation.2 This protective process can be supported or restricted by infection, medication, or mutations.
ICIs support T-cell–mediated destruction of tumor cells by inhibiting the mechanisms designed to limit autoimmunity, specifically the programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) and cytotoxic T-lymphocyte–associated antigen 4 (CTLA-4) pathways. The results have been impressive, leading to an expansive number of US Food and Drug Administration (FDA) approvals across a diverse set of malignancies. Consequently, the Nobel Prize in Physiology or Medicine was awarded for such work in 2018.3
BACKGROUND
While altering these pathways has been shown to hinder tumor growth, the lesser restrictions on the immune system can drive unwanted autoimmune inflammation to host tissue. These toxicities are collectively known as immune-mediated adverse reactions (IMARs). Clinically and histologically, IMARs frequently manifest similarly to other autoimmune conditions and may affect any organ, including skin, liver, lungs, heart, intestine (small and large), kidneys, eyes, endocrine glands, and neurologic tissue.4,5 According to recent studies, as many as 20% to 30% of patients receiving a single ICI will experience at least 1 clinically significant IMAR, and about 13% are classified as severe; however, < 10% of patients will have their ICIs discontinued due to these reactions.6
Though infrequent, a thorough understanding of the severity of IMARs to ICIs is critical for the diagnosis and management of these organ-threatening and potentially life-threatening toxicities. With the growing use of these agents and more FDA approvals for dual checkpoint blockage (concurrent use of CTLA-4 and PD-1/PD-L1 inhibitors), the absolute number of IMARs is expected to rise, thereby leading to more exposure of such events to both oncology and nononcology clinicians. Prior literature has clearly described the treatments and outcomes for many common severe toxicities; however, information regarding presentations and outcomes for rare IMARs is lacking.7
A few fascinating cases of rare toxicities have been observed at the New Mexico Veterans Affairs Medical Center (NMVAMC) in Albuquerque despite its relatively small size compared with other US Department of Veterans Affairs medical centers. As such, herein, the diagnostic evaluation, treatments, and outcomes of rare IMARs are reported for each case, and the related literature is reviewed.
Patient Selection
Patients who were required to discontinue or postpone treatment with any ICI blocking the CTLA-4 (ipilimumab), PD-1 (pembrolizumab, nivolumab, cemiplimab), or PD-L1 (atezolizumab, avelumab, durvalumab) pathways between 2015 to 2021 due to toxicity at the NMVAMC were eligible for inclusion. The electronic health record was reviewed for each eligible case, and the patient demographics, disease characteristics, toxicities, and outcomes were documented for each patient. For the 57 patients who received ICIs within the chosen period, 11 required a treatment break or discontinuation. Of these, 3 cases were selected for reporting due to the rare IMARs observed. This study was approved by the NMVAMC Institutional Review Board.