Oncology Clinical Trials: Key Endpoints

 


In oncology clinical trials, various endpoints are used to evaluate treatment efficacy. These can be classified into tumor response-based, time-to-event, and patient-reported endpoints.

1. Tumor Response-Based Endpoints

a. Overall Response Rate (ORR)

  • Definition: The proportion of patients with a confirmed complete response (CR) or partial response (PR) based on RECIST criteria.
  • Formula: ORR=CR+PRTotal Patients Assessed×100
  • Significance: A key efficacy measure, often used in early-phase trials.

b. Best Overall Response (BOR)

  • Definition: The best response (CR, PR, stable disease [SD], or progressive disease [PD]) observed in a patient at any time during the trial.
  • Interpretation: Shows the maximum effect of the treatment.

c. Duration of Response (DOR)

  • Definition: The time from first confirmed response (CR or PR) until disease progression or death.
  • Significance: Measures how long a patient benefits from the therapy.
  • Example: If DOR = 8.5 months, it means patients maintained their tumor response for a median of 8.5 months.

2. Time-to-Event Endpoints

a. Progression-Free Survival (PFS)

  • Definition: The time from randomization/treatment start until disease progression or death.
  • Interpretation: Higher PFS indicates better disease control.
  • Common in: Phase 2 and 3 trials.

b. Overall Survival (OS)

  • Definition: The time from randomization/treatment start until death from any cause.
  • Significance: The gold standard for evaluating survival benefit.

c. Event-Free Survival (EFS)

  • Definition: Time from treatment start until disease progression, relapse, or death, whichever occurs first.
  • Difference from PFS: EFS includes events beyond RECIST-defined progression, such as relapse in localized disease.

d. Time to Treatment Failure (TTF)

  • Definition: Time from treatment start to discontinuation due to any reason, including progression, toxicity, or patient withdrawal.
  • Broader than PFS, as it includes treatment intolerance.

3. Other Important Endpoints

a. Disease Control Rate (DCR)

  • Definition: The percentage of patients with CR, PR, or SD.
  • Formula: DCR=CR+PR+SDTotal Patients Assessed×100%DCR = \frac{\text{CR} + \text{PR} + \text{SD}}{\text{Total Patients Assessed}} \times 100\%
  • Significance: Reflects both tumor shrinkage and disease stabilization.

b. Time to Response (TTR)

  • Definition: The median time from treatment initiation to first documented tumor response (CR or PR).
  • Clinical use: Indicates how quickly a therapy starts working.

c. Quality of Life (QoL)

  • Definition: A patient-reported endpoint assessing symptoms, functional status, and overall well-being.
  • Common tools: EORTC QLQ-C30, FACT-G.

Summary Table

EndpointDefinitionKey Interpretation
ORR% of patients achieving CR or PRMeasures tumor shrinkage
BORBest tumor response during trialMaximum observed effect
DORTime from first response to progression/deathHow long the response lasts
PFSTime to progression or deathDisease control measure
OSTime to death from any causeGold standard for survival
EFSTime to progression, relapse, or deathBroad measure of treatment effect
TTFTime to treatment discontinuationIncludes toxicity and intolerance
DCR% of patients with CR, PR, or SDIncludes stable disease
TTRTime from treatment to first responseHow fast a drug works
QoLPatient-reported quality of lifeAssesses treatment impact beyond survival

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