Keytruda (pembrolizumab) is an immune checkpoint inhibitor. In breast cancer, it is used in combination with chemotherapy in some settings. Many side effects are immune-related and different from chemotherapy’s effects. Management depends on the type and severity of the side effect, which your oncology team will tailor to you. Here’s a practical overview to help you understand how these are usually managed.
Important quick notes
- Always report new or worsening symptoms to your oncology team promptly.
- Side effects are usually graded 1 to 4 (mild to life-threatening). Management changes with the grade.
- Some side effects look like other illnesses (infection, stomach flu, etc.). Your team may test for other causes to guide treatment.
- Do not stop Keytruda or change doses without talking to your oncologist.
What your team will monitor
- Regular blood tests: liver enzymes (AST/ALT), kidney function (creatinine, BUN), electrolytes, blood counts, thyroid tests (TSH, free T4).
- For thyroid issues, they may check thyroid function periodically even if you feel fine.
- If you develop symptoms suggestive of lung, gut, liver, or endocrine problems, they may order imaging or additional labs.
Common side effects and general management
- Fatigue, mild fever, or low energy: often improves with time; rest, hydration, and talking with your team about treatment timing.
- Rash or itching (skin): moisturizers, cool compresses, and low-dose topical steroids for mild rashes. If widespread or blistering, or if it involves the mouth or eyes, contact your doctor.
- Diarrhea or stomach upset: stay hydrated; anti-diarrheal medicines (like loperamide) can help for mild symptoms. If diarrhea is moderate to severe or persistent, your team may hold Keytruda and start steroids if it’s immune-related.
- Nausea or mild vomiting: anti-nausea medicines as prescribed; hydration is important.
- Cough, shortness of breath, or chest pain: needs prompt evaluation to rule out pneumonitis or infection.
- Joint or muscle aches: acetaminophen or NSAIDs may help if approved by your doctor; persistent pain should be discussed.
- Infusion reactions (during or soon after a drip): symptoms like fever, chills, flushing, or trouble breathing require immediate medical attention; your team may adjust future infusions.
Immune-related adverse events (irAEs) by organ system
These are immune-driven and can be serious. Management often involves holding Keytruda and starting steroids (or other immune-modulating medicines). Examples:
- Gastrointestinal (colitis/diarrhea)
- Grade 1: mild, may continue with symptomatic care.
- Grade 2: hold Keytruda; start prednisone or equivalent if symptoms persist.
- Grade 3–4: hold or discontinue Keytruda; start higher-dose steroids (e.g., prednisone 1 mg/kg/day or IV methylprednisolone) and consult a gastroenterologist.
- Liver inflammation (hepatitis)
- Elevations in liver enzymes: hold Keytruda; start steroids. Most recover with treatment, then taper steroids over weeks.
- Pneumonitis (lung inflammation)
- Cough or shortness of breath: hold Keytruda; evaluate with imaging. Grade 2 usually needs steroids; higher grades may require permanent discontinuation and urgent care.
- Endocrine problems (thyroid, adrenal, pituitary)
- Hypothyroidism or hyperthyroidism: may need thyroid hormone replacement or other treatment; Keytruda can usually be continued if symptoms are manageable.
- Adrenal insufficiency or other hormone problems: may require steroids and endocrine specialist input; some conditions need ongoing hormone replacement.
- Skin (severe rash, blistering)
- Mild rash: topical care.
- Severe rash or Stevens-Johnson-like symptoms: hold/discontinue therapy and treat urgently with steroids and dermatology input.
- Kidney inflammation (nephritis)
- Hold therapy; steroids if indicated; monitor kidney function.
- Eye or nervous system inflammation
- Can occur but are less common; require specialist input (ophthalmology or neurology) and careful management.
Breast cancer-specific and practical considerations
- If Keytruda is given with chemotherapy, some side effects come from chemo as well (low blood counts, mucositis, neuropathy). Your team will help distinguish which symptoms come from which treatment and adjust plans accordingly.
- Steroid use to treat irAEs can have side effects (weight gain, mood changes, sleep problems, high blood sugar, increased infection risk). Your team will try to use the lowest effective dose and taper as symptoms improve.
- Endocrine issues often require long-term management (e.g., thyroid hormone replacement). Your care team may continue Keytruda while you manage the endocrine condition, depending on severity.
- Vaccines: live vaccines are usually avoided during immune therapy. Discuss with your oncology team about recommended vaccines (e.g., flu shot) and timing.
What to do if you have symptoms
- Track symptoms day by day (what started, how bad it is, and how long it lasts).
- Call or message your oncology team promptly for new or worsening symptoms, especially:
- Severe diarrhea (more than 4 stools a day with or without blood)
- Severe abdominal pain, vomiting, or fever
- Shortness of breath, chest pain, new cough
- Severe jaundice (yellow skin/eyes), dark urine
- Severe rash, blistering, or mucous membrane involvement
- Severe headaches, vision changes, confusion
- Symptoms suggesting adrenal or thyroid problems (unexplained fatigue, dizziness, fainting, weight changes, intolerance to heat or cold)
Emergency signs
- You should seek urgent care if you have chest pain, trouble breathing, severe abdominal pain, or sudden severe weakness or confusion.
What to discuss with your doctor
- All medications and supplements you’re taking (some can affect immune therapy or raise infection risk).
- History of autoimmune diseases or previous irAEs.
- Pregnancy or nursing status.
- Any prior reactions to infusions or other medicines.
- Your feelings about treatment goals, and any concerns about side effects.
Bottom line
- Side effects from Keytruda are often manageable with careful monitoring and timely treatment.
- Most immune-related side effects are reversible if caught early and treated properly.
- Your oncology team will tailor monitoring and treatment to your specific situation, balancing cancer control with quality of life.
If you’d like, tell me what breast cancer setting you’re in (e.g., combination with chemo, specific regimen, or stage) and any symptoms you’re experiencing. I can tailor this further and break down what to watch for in your particular plan. However, for any new or worsening symptoms, contact your healthcare team promptly. This information is general and not a substitute for medical advice from your doctors.