CTCAE stands for Common Terminology Criteria for Adverse Events and is the National Cancer Institute’s standardised system for naming and grading adverse events in oncology trials. For each event, CTCAE describes severity grades from 1 to 5, where these are defined for the relevant term. The scale ranges from mild events to death related to the adverse event.
Structure of the CTCAE system
CTCAE includes event terms with assigned severity-grade definitions and is provided by the NCI’s Cancer Therapy Evaluation Program. Version 5.0 was published on November 27, 2017; NCI now also provides CTCAE v6.0. The version applicable under the respective protocol must therefore be stated unambiguously.
The grades are not merely a verbal scale; for each event they are tied to clinical criteria. Grade 1 denotes mild findings, Grade 2 moderate, and Grade 3 severe or medically significant findings; Grade 4 stands for life-threatening consequences requiring urgent intervention. Grade 5 means death related to the adverse event. Not every CTCAE term includes all grades.
Assessing events in day-to-day trial conduct
A CTCAE assignment requires sufficiently specific clinical documentation, for example on symptoms, findings, interventions and functional impairment. The grade should be assigned based on the definition of the applicable term, rather than derived from a general impression. If findings change, the event course and the highest grade reached must remain traceable over time.
CTCAE supports comparable capture of oncologic toxicities, but it replaces neither medical judgement nor causality assessment. An event may be severe by CTCAE and still not qualify as a serious adverse event; conversely, an event with a lower CTCAE grade may be serious due to hospitalisation or other criteria. These two axes must be documented separately.
Distinguishing CTCAE from MedDRA and GCP severity
MedDRA is a medical terminology used to code reported events and analyse them hierarchically. CTCAE is not a second dictionary for MedDRA, but an oncology terminology with event-specific grade definitions. CTCAE terms are organised by MedDRA system organ classes, but this does not mean the coding function and the grading function are equivalent.
The GCP-relevant assessment of an event’s severity concerns its intensity; the assessment of seriousness asks whether statutory criteria such as death, life-threatening condition or hospitalisation are met. CTCAE provides a standardised intensity grading, but it does not, on its own, determine reporting as an SAE. The entry unerwuenschtes-ereignis addresses the general safety category, whereas CTCAE specifies the oncologic grading logic.
Keeping the terms “severe” and “serious” separate helps prevent a common documentation error. A CTCAE Grade 3 can be medically significant without meeting any of the criteria for a serious adverse event. Conversely, a Grade 2 event can trigger an unplanned hospitalisation and then require an SAE assessment. CTCAE grade must also be distinguished from causality assessment: it rates the intensity of the event, not its relationship to the study treatment. For safety listings, the event term, CTCAE grade, causality, expectedness and SAE status should therefore be maintained as separate, auditable data points. Especially in immunotherapies, this differentiation can substantially facilitate consistent medical assessment across sites.
For coding within the data flow, a MedDRA mapping may be required in addition to CTCAE. Both entries must complement each other in a content-plausible way, but they serve different analysis purposes. The system organ classes in CTCAE support medical orientation; however, they do not make CTCAE a licensing or versioning alternative to MedDRA. If an event is maintained in both systems, the study documentation should specify which team is responsible for reviewing the CTCAE term and which team is responsible for reviewing the MedDRA coding.
Relevance for clinical trials
The statistical analysis plan should specify the CTCAE version, grading responsibilities, and how start, end and maximum grade are captured. eCRFs must capture the associated clinical information so that data management and medical monitoring can perform a plausibility check between term, grade, action and course. When versions change, different criteria must not be used unnoticed within the same analysis.
Full-service CROs such as Mediconomics support the transfer of CTCAE requirements into safety sections, eCRFs and data validation rules. They train project teams on separating CTCAE grade from SAE assessment, coordinate medical data review, and support medical writing with tables in which event terms, highest grades, frequencies and serious events are transparently kept distinct.
Frequently Asked Questions (FAQ)
Is Grade 5 in CTCAE a particularly intensive intervention?
No. Grade 5 denotes death related to the adverse event. Grade 4, by contrast, describes life-threatening consequences for which urgent intervention is indicated.
Can a CTCAE grade replace the SAE assessment?
No. Grading measures intensity based on a term definition. Classification as serious follows additional reporting criteria and must be assessed separately.
Why must the CTCAE version be stated in the protocol?
CTCAE continues to evolve. The named version determines which terms and grade definitions are used for collection, data review and analysis.
Regulatory References
- NCI Common Terminology Criteria for Adverse Events, Version 5.0 – includes event terms and grade definitions.
- NCI CTCAE and AE Reporting – provides versions and materials for AE assessment.
- ICH E6(R3) Good Clinical Practice – embeds the reliable collection and reporting of safety data.