Researchers from Mass General Brigham have published new findings on a rare complication associated with immune checkpoint inhibitors (ICIs), a type of cancer immunotherapy. The study, which appears in Blood and was presented at the American Society of Hematology Annual Meeting, is the first large-scale analysis to detail risk factors and outcomes for ICI-associated immune thrombocytopenia (ICI-ITP).
ICI-ITP is an autoimmune condition where platelet counts fall to dangerously low levels. While ICIs have transformed cancer treatment, their use can sometimes lead to immune-related side effects such as ICI-ITP, which remains poorly understood due to its rarity.
Lead author Rebecca Karp Leaf, MD, a hematologist at the Mass General Brigham Cancer Institute, explained the scope of the research: "We worked with colleagues at Mass General Brigham and with collaborators from six other major academic cancer centers across the U.S. to query the records of over 86,000 patients who received ICI therapy between 2016 and 2023, ultimately identifying 214 patients-or 0.25%–who developed ICI-ITP."
The study found that patients who developed ICI-ITP often had lower platelet counts before starting treatment, were more likely to receive multiple classes of ICIs, had advanced stage 4 cancer, and experienced other immune-related adverse events. The onset of ICI-ITP typically occurred around eight weeks after beginning therapy.
Treatment for affected patients included glucocorticoids, immune globulin, and thrombopoietin receptor agonists. Recovery was seen in about three-quarters of cases within just over two weeks on average. Of those who resumed ICI therapy after initial treatment for ICI-ITP, nearly one-third experienced a recurrence.
Senior author David Leaf, MD, MMSc, FASN commented on these findings: "We found that nearly 70% of patients who were rechallenged with ICIs after an initial episode of ICI-ITP did not develop of this immune-related adverse event, which provides reassuring evidence that, with careful monitoring, ICI rechallenge is feasible for most patients."
The research also showed that both the presence and severity of ICI-ITP were linked to an increased risk of death among cancer patients receiving ICIs. Those with severe forms faced almost three times higher mortality compared to those without this complication. This highlights the need for early detection and prompt management in affected individuals.
