Side Effects in Clinical Trials

There are special terms used for talking about side effects in clinical trials. The side effect of a treatment during clinical trials is called an adverse event (AE). An adverse event can occur from using a drug during a clinical trial. It is an unfavorable or unintended sign, symptom, or disease that is associated with an investigational treatment.

 The National Cancer Institute (NCI) measures the seriousness of an adverse event using the Common Toxicity Criteria for Adverse Events (CTCAE).

Grading of Adverse Events

Adverse events are graded on a scale from 1 to 5 as follows:

• Grade 0 refers to not having a symptom or problem, so someone with grade 0 pain has no pain at all.
• Grade 1 adverse events are mild and generally not bothersome.
• Grade 2 events are bothersome and may interfere with doing some activities but are not dangerous. They may significantly impact the patient’s quality of life.
• Grade 3 events are serious and interfere with a person’s ability to do basic things like eat or get dressed. Grade 3 events may also require medical intervention.
• Grade 4 events are usually severe enough to require hospitalization.
• Grade 5 events are fatal.

Doctors over a clinical trial assess adverse events at each stage of a clinical trial.

Using headaches as an example, here is what various adverse event grades could look like:

• A grade 1 headache is mild.
• A grade 2 headache keeps the patient from doing things like shopping or cooking.
• A grade 3 headache keeps the patient from getting out of bed even to go to the bathroom.

When it comes to side effects, most clinical trials and doctors focus on grade 3 or higher events. This is because those are the most dangerous side effects.