Common Terminology Criteria for Adverse Events v5.0 (CTCAE v5.0)

The NCI Common Terminology Criteria for Adverse Events (CTCAE) version 5.0, published November 2017, is the universal standard for grading and communicating adverse events in oncology clinical trials and clinical practice. It provides a standardized vocabulary and severity scale (Grades 1–5) for over 800 adverse event terms organized across 26 System Organ Classes (SOCs). Each CTCAE grade represents a defined severity tier from mild (Grade 1) through death (Grade 5), with specific grade-specific descriptions for each individual adverse event. CTCAE is required by FDA and EMA for all oncology trial safety reporting, informs dose modification algorithms, and drives real-time clinical management decisions. Grade 3–4 adverse events are the primary safety endpoints that trigger protocol-specified dose reductions, delays, or discontinuations.

Toxicity Grading — CTCAE v5.0 Criteria

• 1: Mild — Mild; asymptomatic or mild symptoms; clinical or diagnostic observations only; intervention not indicated. The adverse event is transient and does not interfere with normal daily activities. Continue therapy at current dose. Initiate appropriate supportive care (e.g., antiemetics, loperamide, topical agents) as indicated. Counsel patient on self-monitoring and when to contact the clinical team. Document and monitor at each visit.
• 2: Moderate — Moderate; minimal, local, or noninvasive intervention indicated; limiting instrumental activities of daily living (ADLs) such as preparing meals, shopping, managing money, housework, transportation. Continue therapy with intensified supportive management. Consider dose delay if Grade 2 toxicity persists beyond the expected recovery period or is worsening. Resume therapy when toxicity resolves to Grade ≤1 — a dose reduction is not always required at Grade 2 but should be considered for persistent toxicity. Evaluate whether to add prophylactic supportive measures going forward.
• 3: Severe — Severe or medically significant but not immediately life-threatening; hospitalization or prolongation of hospitalization indicated; disabling; limiting self-care ADLs such as bathing, dressing, feeding, toileting, or continence. Hold cancer-directed therapy. Treat the adverse event — hospitalization is frequently required. Upon recovery to Grade ≤1 (or Grade ≤2 for selected toxicities per protocol), resume therapy at a protocol-specified dose reduction (typically one dose level). Document as a serious adverse event (SAE) if hospitalization required. Permanently discontinue for Grade 3 immune-mediated toxicities in most immunotherapy protocols.
• 4: Life-Threatening — Life-threatening consequences; urgent intervention indicated. The adverse event poses an immediate threat to the patient's life and requires acute medical intervention. Permanently discontinue therapy in most protocols — life-threatening toxicity rarely permits re-challenge. Initiate immediate medical management (ICU-level care as required). File an expedited safety report (7-day if unexpected, 15-day if expected) per FDA IND regulations. Multidisciplinary consultation should be urgently arranged.
• 5: Death — Death related to adverse event. Report as a fatal serious adverse event (SAE). An expedited 7-day IND safety report is required for unexpected fatal events. Conduct a comprehensive root-cause analysis. Notify the IRB per institutional policy. Review all concurrent patients on the same regimen for shared risk factors.