Predictors of Long-Term Survival in Patients With Immune Checkpoint Inhibitor-Associated Myocarditis

Immune checkpoint inhibitor-associated myocarditis (ICIM) carries high rates of morbidity and death, but clinical outcomes vary widely. Little is known about the clinical variables associated with long-term survival.

In this case-control study, patients diagnosed with ICIM at Massachusetts General Hospital between 2016 and 2022 were stratified into 3 groups based on length of survival after ICIM diagnosis: short-term (<30 days), intermediate-term (30-365 days), and long-term (>365 days). Baseline characteristics, immune checkpoint inhibitor regimens, laboratory values, ECG parameters, and ICIM treatments were analyzed to identify predictors of long-term survival.

Among 35 patients with ICIM (median follow-up time, 8.3 months), there were 9 (25.7%) in the short-term survival group, 13 (37.1%) in the intermediate-term survival group, and 13 (37.1%) in the long-term survival group. Those in the short-term survival group were older (median age, 82 versus 68 for intermediate-term and 75 for long-term; P=0.003). Using logistic regression, long-term survival was associated with an interval from immune checkpoint inhibitor initiation to ICIM diagnosis ≥75 days (odds ratio, 5.4; P=0.043) and a troponin T decrement ≥42% by day 8 after immunosuppression initiation (odds ratio, 5.5; P=0.042). Using multivariate Cox regression modeling, troponin T≤1000 ng/L (hazard ratio [HR], 4.0; P=0.007) and neutrophil/lymphocyte ratio ≤4.4 (HR, 7.9; P < 0.001) were independently associated with longer survival.

Time to onset of ICIM, multiple clinical tests, and responsiveness to immunosuppressive therapy were associated with long-term survival after ICIM. Consideration of these variables may help with risk stratification and immunosuppressive therapy individualization.