# CTCAE toxicity grading (grade 3-4 adverse events)

Source: https://onco.cc/terms/ctcae-grading/  
OnCo record `ctcae-grading` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The standard 1-to-5 scale doctors use to grade every side effect in a trial: 1 mild, 2 moderate, 3 severe or needing hospital care, 4 life-threatening, 5 death. 'Grade 3-4 events in 40% of patients' is the usual headline safety figure.

## Summary

The NCI Common Terminology Criteria for Adverse Events (now v5.0) defines each toxicity by grade (neutropenia by neutrophil count, diarrhoea by stool frequency, neuropathy by function), allowing comparison across trials. Reports distinguish all-cause adverse events, treatment-related (attributed by the investigator), serious (hospitalisation or worse) and treatment-emergent, and often quote grade ≥3 rates and discontinuations. Limitations: grading is done by clinicians, who under-report symptoms compared with patient-reported PRO-CTCAE; chronic low-grade toxicity of long-term pills is poorly captured by grade alone; and different drugs' grade 3 events are not equally burdensome (asymptomatic lab abnormalities versus disabling neuropathy).

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: CTCAE; Common Terminology Criteria for Adverse Events; grade 3-4; grade 3–4; grade ≥3; grade 3 or higher; grade 3; grade 4; grade 5; grade 1-2; grade 2; high-grade toxicity; severe adverse events; adverse event; adverse events; serious adverse event; serious adverse events; SAE; SAEs; treatment-related adverse events; TRAE; TRAEs; TEAE; TEAEs; treatment-emergent; treatment-related death; treatment-related deaths; toxic death; safety signal; tolerability profile; safety signals

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Common_Terminology_Criteria_for_Adverse_Events
- Wikipedia: https://en.wikipedia.org/wiki/Common_Terminology_Criteria_for_Adverse_Events

## Connected records

- terms: [Dose reduction, interruption and discontinuation](https://onco.cc/terms/dose-modification/), [Dose-limiting toxicity (DLT)](https://onco.cc/terms/dose-limiting-toxicity/), [Immune-related adverse events (irAEs)](https://onco.cc/terms/irae/), [Quality of life and patient-reported outcomes (QoL, PRO)](https://onco.cc/terms/qol-pro/)
- fronts: [Supportive Care & Survivorship](https://onco.cc/fronts/supportive-care/)

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