🧪 Comparative Cohort Study

A comparative cohort study is a type of observational study in which two or more groups (cohorts) of individuals are followed over time and compared based on exposure to different interventions, treatments, or risk factors.

📚 Key Characteristics: Not randomized: Participants are not assigned randomly to groups. The study observes what happens in real-life conditions.

Prospective or retrospective:

Prospective: Groups are followed from the present into the future.

Retrospective: Researchers look back at existing data or records.

Comparison: At least two groups are compared based on a defined variable (e.g., drug A vs. drug B).

Outcomes measured: Includes survival, progression, adverse effects, etc.

🏥 Example (from your study): Patients with hepatocellular carcinoma were divided into two groups based on whether they received lenvatinib or donafenib, and their survival and safety outcomes were compared retrospectively.

⚠️ Limitations: Susceptible to bias (selection bias, confounding).

Cannot establish causality—only associations.

Relies on quality and completeness of available data.