Management of Flu-Like Symptoms After Keytruda (Pembrolizumab)
For mild flu-like symptoms (fever, chills) after pembrolizumab infusion, provide symptomatic treatment with antipyretics and antihistamines while continuing to monitor closely; for moderate symptoms, interrupt or slow the infusion rate; and for severe reactions (Grade 3/4), permanently discontinue pembrolizumab. 1
Understanding the Clinical Context
Flu-like symptoms after pembrolizumab represent infusion-related reactions (IRRs), which occur in approximately 3% of patients receiving this anti-PD-1 therapy 1. The typical presentation includes pyrexia (fever) and chills as the primary manifestations 1. The FDA label confirms that pembrolizumab can cause severe or life-threatening infusion-related reactions, including hypersensitivity and anaphylaxis, though these severe reactions occurred in only 0.2% of 2,799 patients 2.
Immediate Evaluation During or Shortly After Infusion
Monitor for the following signs and symptoms of infusion-related reactions: 2
- Mild symptoms (Grade 1-2): Rigors, chills, fever, pruritus, flushing, rash
- Severe symptoms (Grade 3-4): Wheezing, hypotension, hypoxemia, tachycardia, blood pressure lability, chest pain, cough, shortness of breath, angioedema, presyncope or syncope
The ASCO guidelines note that presenting symptoms related to immune-related infusion reactions typically manifest as low-grade fever, chills, headache, or nausea, while high-grade reactions include additional cardiopulmonary and hemodynamic instability 3.
Grading and Management Algorithm
Grade 1-2 (Mild to Moderate) Reactions:
- Stop or slow the infusion rate 1
- Provide symptomatic treatment with antipyretics (acetaminophen) and antihistamines (diphenhydramine) 1, 3
- Resume infusion with close monitoring once symptoms resolve 1
- Consider premedication with antipyretic and antihistamine for subsequent infusions 1
Grade 3-4 (Severe to Life-Threatening) Reactions:
- Stop the infusion immediately 1
- Provide aggressive symptomatic treatment including IV fluids, corticosteroids if needed, and supportive care 1, 3
- Permanently discontinue pembrolizumab 1, 2
Important Clinical Considerations
Premedication is not routinely recommended for pembrolizumab, but may be considered in patients who have experienced prior infusion reactions 1. This contrasts with other monoclonal antibodies like daratumumab or rituximab that require routine premedication 1.
Distinguish infusion reactions from immune-related adverse events (irAEs): While flu-like symptoms during or immediately after infusion suggest an infusion reaction, similar symptoms developing days to weeks later may represent immune-mediated toxicities requiring different management 3, 2. The FDA label emphasizes monitoring for immune-mediated adverse reactions that can occur in any organ system 2.
Common Pitfalls to Avoid
Do not confuse infusion reactions with infection: Fever and chills after pembrolizumab may mimic infectious processes, but true infusion reactions occur during or within hours of the infusion 1. If symptoms develop days later, consider alternative diagnoses including infection or immune-mediated toxicities 3, 2.
Do not automatically discontinue for mild reactions: Grade 1-2 reactions can be managed with rate reduction and symptomatic treatment, allowing continuation of therapy 1. Only severe Grade 3-4 reactions require permanent discontinuation 1, 2.
Consider cross-reactivity with other PD-1 inhibitors cautiously: While one case report demonstrated successful transition from nivolumab to pembrolizumab after a hypersensitivity reaction 4, this should be approached carefully with appropriate monitoring and premedication, as both agents target the same pathway.
Monitoring After Resolution
For patients who experience mild infusion reactions and continue therapy, consider premedication with antipyretics and antihistamines before subsequent doses 1. The ESMO guidelines support this approach for pembrolizumab, though it is not mandated 1.
Observe patients for a period after infusion completion to ensure no delayed reactions occur, particularly after the first dose when reactions are most common 1.