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Long term follow up (LTFU) in clinical research: What you need to know

February 23, 2023

When it comes to standalone long term follow up (LTFU) studies or ongoing studies requiring long-term follow-up, there can be some confusion or misalignment on commonly used terms and definitions in the space. To address this, Curebase put forth this glossary-style list of frequently used terms and FAQs: 

What is long term follow up?

According to the National Cancer Institute, follow up can be defined as  “monitoring a person's health over time after treatment,” which can include “keeping track of the health of people who participate in a clinical study or clinical trial for a period of time, both during the study and after the study ends.” 

What is long term follow up in clinical trials? 

Long term follow up is the monitoring of a patient’s health over an extended period of time after treatment. The FDA defines LTFU in clinical trials as ”extended assessments that continue some of the scheduled observations of a clinical trial past the active follow-up period, and are an integral portion of the study of some investigational GT products. LTFU observations are important to monitor long term safety of GT products.” 

What is a long term clinical trial? 

Long term follow up may be necessary for low-risk treatments in order to validate safety and explore more information about certain treatments. However, some clinical trials are considered long term clinical trials because the follow up period is much longer than typical trial timelines due to safety risks, complication likelihood, the need for data collection, and many other factors. Trials likely to be considered long term follow up trials after often complex oncology and rare disease treatments. 

What is a long term follow up study?

In most scenarios, a long term follow up study is an extension of a  clinical trial where it becomes obvious there is a need for continued collection of patients’ health information and feedback directly after participation.  For example, patients who have received oncology treatment for cancer may complete their treatment and the active care portion of that trial and then participate in the long term follow up study where they are asked to provide health information for months or years after their treatment. However, it is common to run LTFU trials as standalone studies which incorporate different tools and design necessary for proper study execution. 

How long is long term follow up?

Long term follow up can vary in time frames. Some studies may require 2 or 3 months, while others can last upwards of 10 years. The length of the follow up are all relative to the type of study and the desired purpose intended for running the study. An example of LTFU study protocol is this gene therapy study where long term follow up lasts 5 years after the final study visit to “identify and mitigate long term risks to the participants receiving their gene therapy products.”

Why is long term follow up important in general?

Researchers Hill, K. G., et. al., found some benefits of  long term follow up include  “the capacity to examine program effects across multiple later life outcomes, the ability to examine the etiological processes involved in the development of the outcomes of interest, and the ability to provide more concrete estimates of the relative benefits and costs of an intervention.”

Why is long term follow up important in research?

One of the most widely accepted reasons why LTFU is important in clinical research is to ensure and validate long term safety and effectiveness for all patients who may receive this particular treatment or intervention, such as side effects, interactions with other treatments, etc. There are also several instances where the FDA requires long term follow up studies for specific treatments to be completed in the trial process for a magnitude of reasons. 

A lot of information on LTFU trials can vary from case to case however, having a unified understanding of common terms and questions can benefit all stakeholders participating in and running these trials. 

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