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Incidence, Risk Factors, and Survival Implications of Immune-Related Adverse Events in Patients With Metastatic
Nikita V Baclig1, Madhuri Chengappa2, Andrew J Soliman1
1University of California Los Angeles, Department of Medicine, Los Angeles, CA.
Background:
Immune checkpoint inhibitors (ICIs) are increasingly used in metastatic breast cancer (mBC), yet real-world data on immune-related adverse events (irAEs) are limited.
Patients And Methods:
We conducted a retrospective cohort study across 4 NCI-designated cancer centers. Adults with mBC treated with ICIs between 2014 and 2024 were included. irAEs were defined by provider attribution or treatment with high-dose corticosteroids and exclusion of other clear causes. Predictors of irAE were assessed using multivariable logistic regression. Overall survival (OS) was evaluated using a 12-week landmark analysis.
Results:
Among 522 patients (mean age 55.4), most received pembrolizumab (83.9%) and ICI in combination (82.7%). Over a median follow-up of 17.5 months, 42.5% experienced ≥1 irAE and 13.2% had severe (grade 3-4) events. Lower odds of irAE were observed for Black race (OR 0.43; P = .028), low albumin (OR 0.50; P = .007), and low hemoglobin (Hgb) (OR 0.60; P = .009), while higher odds were associated with age 46-55 (OR 1.76, P = .035), CDK4/6 inhibitor use (OR 1.82; P = 0.030) and ≥4 ICI cycles (OR 1.70; P = .007). Among 332 patients included in the landmark analysis, grade 1-3 irAEs were associated with superior OS compared with no irAE, whereas grade 4 irAEs were associated with inferior OS (log-rank P < .0001).
Conclusion:
In this multi-institutional real-world cohort of mBC patients treated with ICIs, irAEs were more frequent than reported in breast cancer clinical trials. ICI duration and CDK4/6 inhibitor use increased irAE risk, while baseline albumin influenced survival. Mild-to-moderate irAEs were associated with improved outcomes, but severe irAEs portended worse survival. These findings support risk-stratified ICI use in mBC.
Insights
Immune checkpoint inhibitors (ICIs) in metastatic breast cancer (mBC) led to frequent immune-related adverse events (irAEs). Mild irAEs improved survival, but severe irAEs worsened outcomes, suggesting risk-stratified ICI use.
Area of Science:
- Oncology
- Immunotherapy
- Breast Cancer Research
Background:
- Immune checkpoint inhibitors (ICIs) are increasingly utilized for metastatic breast cancer (mBC).
- Real-world data on immune-related adverse events (irAEs) in this population remain limited.
- Understanding irAEs is crucial for optimizing ICI therapy in mBC.
Purpose of the Study:
- To investigate the incidence and predictors of irAEs in patients with mBC treated with ICIs.
- To evaluate the impact of irAEs on overall survival (OS) in this cohort.
- To provide real-world evidence supporting risk-stratified ICI use in mBC.
Main Methods:
- Retrospective cohort study across 4 NCI-designated cancer centers.
- Inclusion of adult patients with mBC treated with ICIs (2014-2024).
- Definition of irAEs based on provider attribution or corticosteroid treatment; assessment of predictors and OS using multivariable logistic regression and landmark analysis.
Main Results:
- 42.5% of 522 patients experienced irAEs, with 13.2% having severe (grade 3-4) events.
- Predictors of lower irAE odds included Black race, low albumin, and low hemoglobin; higher odds were linked to age 46-55, CDK4/6 inhibitor use, and ≥4 ICI cycles.
- Mild-to-moderate irAEs (grade 1-3) correlated with superior OS, while grade 4 irAEs were associated with inferior OS.
Conclusions:
- Real-world irAE incidence in mBC patients treated with ICIs exceeds clinical trial reports.
- ICI duration and CDK4/6 inhibitor use increase irAE risk; baseline albumin impacts survival.
- Mild irAEs suggest improved outcomes, whereas severe irAEs indicate worse survival, supporting risk-stratified ICI application.
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