whileontreatment

Whileontreatment is a term used in clinical research to describe the period during which a participant receives a specific medical intervention. It denotes exposure to therapy and is distinguished from periods after treatment discontinuation. Whileontreatment data are used to analyze outcomes that occur while the patient remains on the therapy.

In trial design and analysis, whileontreatment or on-treatment analyses focus on events that happen during active exposure, contrasting with intention-to-treat analyses that follow participants from randomization regardless of treatment status. Endpoints such as progression-free survival, time to treatment discontinuation, and adverse events can be defined within the whileontreatment window. The definition of when treatment starts and ends—often based on dosing records, scheduling, or predefined discontinuation—determines the analysis period.

Limitations and biases: On-treatment analyses can be affected by informative censoring, as patients who discontinue may differ systematically from those who continue. Also, immortal time bias can arise if exposure is misclassified. Therefore, whileontreatment results should be interpreted in the context of exposure definitions and complemented by other analyses.

Practical aspects: Researchers predefine the exposure window, handle dose interruptions, and employ time-varying covariates or as-treated models as appropriate. In clinical practice, whileontreatment insight helps assess real-world drug safety and effectiveness during active use.