Clinical trials are the foundation of evidence-based cancer treatment, yet their listings can be dense and difficult to interpret. Whether you are a healthcare professional evaluating emerging data, a researcher tracking the treatment pipeline, or a patient exploring options, understanding how to read clinical trial information is an essential skill. This guide breaks down the key elements of clinical trial listings as they appear on ClinicalTrials.gov and in our PipelineEvidence database.
Trial Phases Explained
Clinical trials proceed through a structured sequence of phases, each with distinct goals. Phase 1 trials are the first-in-human studies, enrolling small numbers of patients (typically 15-30) to determine safe dosing and identify side effects. These trials often use dose escalation designs where successive groups of patients receive increasing doses. The primary goal is safety, not efficacy. Phase 2 trials evaluate whether the drug shows activity against the cancer, typically enrolling 30-100 patients at the recommended phase 2 dose. Response rate is usually the primary endpoint. Promising phase 2 results justify investment in larger phase 3 studies.
Phase 3 trials are large, randomized studies (typically hundreds to thousands of patients) comparing the new treatment to the current standard of care. These trials generate the pivotal evidence required for FDA approval and practice change. Phase 3 trials typically use overall survival (OS) or progression-free survival (PFS) as primary endpoints. Phase 4 studies monitor safety and effectiveness after FDA approval in the real-world setting.
Understanding Study Design
The gold standard in clinical trial design is the randomized, double-blind, placebo-controlled trial, where patients are randomly assigned to receive the experimental treatment or the control (current standard or placebo) and neither patients nor investigators know who received which. Randomization minimizes selection bias, while blinding prevents observation bias. Open-label trials, where treatment assignment is known, are used when blinding is impractical (e.g., different routes of administration).
Basket trials test a single drug across multiple cancer types sharing a common molecular alteration (e.g., pembrolizumab in all MSI-H cancers). Umbrella trials test multiple drugs in a single cancer type, matching patients to treatments based on their tumor's molecular profile. Adaptive trials use interim data analysis to modify the trial (dropping ineffective arms, adding new arms) while ongoing.
Key Endpoints to Understand
Overall Survival (OS) measures time from randomization to death from any cause and is the gold standard endpoint. Progression-Free Survival (PFS) measures time until disease progression or death and is available earlier. Objective Response Rate (ORR) is the percentage of patients with tumor shrinkage, used for accelerated approval. Duration of Response (DoR) measures how long responses last. Disease-Free Survival (DFS) is used in adjuvant trials measuring time after surgery until recurrence.
The hazard ratio (HR) is a critical statistical measure in time-to-event endpoints. An HR of 0.70 means the experimental treatment reduces the risk of the event (death or progression) by 30% compared to the control. An HR below 1.0 favors the experimental treatment; the further below 1.0, the larger the benefit. The p-value indicates statistical significance (typically p less than 0.05), while the confidence interval (CI) provides the range of plausible treatment effects.
Navigating ClinicalTrials.gov
Each trial on ClinicalTrials.gov is identified by an NCT number (e.g., NCT03036488). Key sections to review include the Brief Summary (overview of hypothesis and design), Eligibility Criteria (who can enroll), Arms and Interventions (what treatments are being compared), and Primary and Secondary Outcome Measures (what endpoints are being evaluated and when results are expected).
PipelineEvidence integrates clinical trial data from ClinicalTrials.gov across all 50 tumor types, with direct links to trial listings. Each tumor page includes active Phase 1, 2, and 3 trials to help clinicians and researchers stay current with the evolving treatment landscape.