Introduction: Patients receiving tumor-infiltrating lymphocyte (TIL) therapy often require ICU admission for monitoring during administration of high-dose interleukin-2 (IL2), which is given to support T cell activity. This case series describes potential IL2-related toxicities, including capillary leak syndrome (CLS), observed during patients’ ICU admission.
Methods: Case series including adults administered commercially available TIL therapy who received ≥1 dose of IL2 in the ICU at Mayo Clinic in Rochester, MN from November 2024 to July 2025. We assessed potential reactions including fever, vasopressor need, cardiac toxicity, and new respiratory support. Potential toxicities were reviewed in real time before proceeding with additional IL2 doses. CLS grade, antibiotic changes, and positive cultures were recorded. Data is summarized using medians and interquartile ranges.
Results: Fourteen patients met inclusion criteria and received a median 3.5 (3, 5) IL2 doses. The most common reactions were fever (79%) and arrhythmia (71%), mostly sinus tachycardia (70%), with 1 patient experiencing self-terminating supraventricular tachycardia. ECG changes were observed in 3 patients, 1 of whom had an S-T elevation myocardial infarction. Only 1 patient required >3L nasal cannula for respiratory support and 4 required pressors for a median of 8 (6, 12.5) hours. Antibiotics (non-prophylaxis) were started or escalated in 10 of 14 patients while in the ICU. Only 2 had positive cultures and de-escalation occurred in 3 patients during their ICU admission. CLS grades 3 and 4 occurred in 4 (29%) and 6 (43%) of patients, respectively. Other toxicities (e.g. transaminitis) were rare.
Conclusions: As TIL therapy becomes more widespread, it is crucial for the ICU team to be aware of potential IL2-related toxicities. This case series demonstrates a high incidence of fever, arrhythmias, and CLS grades 3 and 4. While serious adverse events occurred, most patients required minimal respiratory or cardiovascular support, suggesting adverse effects were generally manageable and transient.
