Rare Blood Disorder Linked to Cancer Immunotherapy Identified in Large-scale Study
A new analysis of over 86,000 patients reveals critical risk factors and treatment strategies for ICI-associated immune thrombocytopenia, a possibly life-threatening complication of advanced cancer care.
A comprehensive study led by researchers at Mass General Brigham has shed light on immune checkpoint inhibitor-associated immune thrombocytopenia (ICI-ITP). This condition, characterized by dangerously low platelet counts, has historically been poorly understood. The findings, published in Blood and presented at the American Society of hematology Annual Meeting, provide the first large-scale description of its risk factors, clinical course, and underscore the vital importance of early diagnosis and treatment.
Understanding the Rise of Immunotherapy and its Challenges
Immune checkpoint inhibitors (ICIs) have dramatically altered the landscape of cancer treatment in recent years.Though, these powerful therapies can sometimes trigger the immune system to attack healthy cells, leading to autoimmune side effects. ICI-ITP is among these immune-related adverse events, and its rarity has made it tough to study until now.
“We worked with colleagues at Mass General Brigham and 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,” explained a lead author of the study, a hematologist with the Mass General Brigham cancer Institute. “Ultimately, we identified 214 patients – or 0.25% – who developed ICI-ITP.”
Key Risk Factors for ICI-ITP
The research team identified several factors that appear to increase a patient’s risk of developing ICI-ITP. These include:
- Lower platelet counts at the start of ICI treatment.
- Receiving immunotherapy regimens that included multiple ICI drug classes.
- Having stage 4 cancer.
- Experiencing other immune-related adverse events concurrently.
ICI-ITP typically occurred at a median of eight weeks after the initiation of ICI therapy. Treatment strategies employed included glucocorticoids, immune globulin, and thrombopoietin receptor agonists. The study showed that recovery occurred in 161 patients (75.2%) at a median of 2.3 weeks.
Rechallenging ICIs After Treatment: A Path Forward?
A significant finding of the study was the feasibility of resuming ICI therapy in many patients after triumphant treatment for ICI-ITP. Of the 76 patients who were restarted on ICIs, 23 (30.3%) experienced a recurrence of the condition.
“We found that nearly 70% of patients who were rechallenged with ICIs after an initial episode of ICI-ITP did not develop this immune-related adverse event,” stated a senior author, Director of Clinical and Translational Research in Acute Kidney Injury in the Division of Renal Medicine in the Mass General Brigham Department of Medicine. “This provides reassuring evidence that, with careful monitoring, ICI rechallenge is feasible for most patients.”
Severity and Mortality Risk
The study also revealed a concerning link between the severity of ICI-ITP and patient mortality. Individuals with severe ICI-ITP faced a nearly three-fold higher risk of death compared to those who did not develop the condition. This finding reinforces the critical need for prompt recognition and treatment of ICI-ITP.
The research underscores the importance of vigilant monitoring for signs of ICI-ITP in patients undergoing immunotherapy, especially those with pre-existing risk factors. Early intervention and careful consideration of ICI rechallenge strategies are crucial for optimizing patient outcomes in this evolving landscape of cancer care.
Source: Rebecca Karp Leaf et al, Immune thrombocytopenia in patients treated with immune checkpoint inhibitors, Blood journal (2025). DOI: 10.1182/blood.2025031449
