Backfilling in early-phase oncology trials: A patient perspective on dose-finding innovation
Presenter: Kirstin Spencer, BS Session: Advocates Poster Session 1 Time: 4/20/2026 2:00:00 PM → 4/20/2026 5:00:00 PM
Authors
Kirstin Spencer Advocate, Winchcombe, United Kingdom
Abstract
Early-phase clinical trials aim to identify safe andeffective dosing strategies, balancing anti-tumour activity with acceptabletoxicity from both clinical and patient perspectives. Historically,dose-finding studies have largely focused on identifying the highest dose thatcan be safely tolerated. However, with targeted therapies and immunotherapies,the goal has increasingly shifted toward identifying doses that maintainbiological activity while keeping side effects acceptable. minimisingunnecessary toxicity and keeping side effects acceptable.“Backfilling” refers to the concurrent enrolment ofadditional patients at lower dose levels, which have already shown to be safe,while a higher dose is currently tested. This enables deeper understanding ofdrug behaviour, anti-cancer activity, and interactions with metabolic andbiological markers, supporting more confident selection of the most appropriatedose for later-phase trials. Importantly, many therapies demonstrate differentbiological effects across dose ranges, meaning that collecting data acrossmultiple dose levels may reveal activity that would not be evident ifdose-finding focused only on identifying the highest tolerated dose.Recent regulatory initiatives and guidance supporting doseoptimisation reflect this evolving approach. The United States of America Foodand Drug Administration (FDA, 2024) and the Methodology for the Development ofInnovative Cancer Therapies (MDICT) Taskforce (2022) both encourage dosefinding studies to consider broader information/evidence than toxicity aloneand highlight the value of backfilling in generating richer datasets collectingadditional information that will ultimately help selecting the optimal dose.From a patient-advocate perspective, backfilling is morethan a technical refinement. It is a practical strategy that widens recruitmentopportunities and allows additional information to be gathered earlier in drugdevelopment. This can help identify effective and tolerable dosing sooner andreduce delays caused by needing additional trials to redefine the appropriatedose. By improving understanding of how treatments behave across dose levels,backfilling may help reduce unnecessary toxicity and metabolic stress.Integrating patient perspectives into trial methodology discussions cantherefore help ensure dose-finding strategies are not only scientificallyrobust but also better aligned with tolerability and real-world patientexperience, enabling kinder, better-tolerated treatments for both current andfuture patients.
Disclosure
K. Spencer, None.
Cited in
Control: 13068 · Presentation Id: 12863 · Meeting 21436