Tests and Monitoring — While on Cetuximab

What tests will you have, and what does each one check?

1. Electrolyte blood test (magnesium, potassium, calcium)

   This is the monitoring most specific to cetuximab. The drug commonly lowers magnesium in the blood, and potassium and calcium can also fall. Your team checks these before most infusions. A low magnesium result usually means replacement is given through a drip before your next infusion. If your magnesium stays very low despite replacement, your team may pause treatment while levels recover. Tell your team about muscle cramps, tingling, or an irregular heartbeat between visits — these can be signs that your electrolytes need checking sooner.

2. Full blood count

   Cetuximab is not a chemotherapy drug and does not usually cause the sharp falls in blood cells that chemotherapy does. Your team will still check your red cells, white cells and platelets before infusions. A falling red cell count can cause increasing tiredness. If yours drops significantly, your team will decide whether a rest from treatment or another approach is needed.

3. Liver function tests

   Your liver is occasionally affected by cetuximab. Enzyme levels are checked at baseline and at intervals during treatment. A mild rise often settles without any change to your treatment. A significant or rising result will prompt your team to pause and investigate before continuing.

4. Monitoring during each infusion

   Your blood pressure, heart rate and oxygen level are checked throughout every infusion. The risk of a serious reaction — flushing, difficulty breathing, or a sudden drop in blood pressure — is highest with the first dose. Your team gives you antihistamine medication before the infusion and gives the first dose more slowly for this reason. A mild reaction can often be managed by slowing the drip. A severe reaction means cetuximab is stopped and not restarted.

5. Skin and nail assessment at every visit

   An acneiform rash on the face, scalp and upper body is one of the most common effects of cetuximab. Your team grades it at each visit. Mild to moderate rash is managed with moisturisers, sunscreen and sometimes a short antibiotic course, and treatment continues. A severe rash means cetuximab is paused until the skin recovers. Nail changes and dry or cracked skin are also noted and treated.

How often will the blood tests happen?

What happens if a test result is abnormal?

Did you know?

Source: ESMO Clinical Practice Guidelines for the management of EGFR inhibitor-related toxicities