Validating a Patient-Centered Measure of Treatment Tolerability in Cancer Care

The Modus Solution

Research consultancy specializing in patient-centered outcomes, helping life sciences organizations measure and understand treatment experiences through qualitative and quantitative research.

HOW WE DID IT

Overview

As part of the LIBRETTO-531 trial, the client needed to strengthen a comparative tolerability endpoint.

While side effects are a critical driver of treatment decisions, existing measures must be validated to ensure they accurately reflect

• Patient-perceived burden
• Real-world tolerability thresholds
• Decision points like dose modification or discontinuation

DELIVER

Our Approach

We designed a qualitative study to ground measurement in patient experience and interpretation. Our work included:

• Concept elicitation interviews
  Exploring how patients define and experience side-effect burden and tolerability
• Cognitive interviews
  Testing how patients interpret the FACT-GP5 item and its response scale
• Targeted probing
  Identifying which response levels correspond to meaningful thresholds (e.g., high burden, treatment change)

The study included 40 patients with MTC participating in the LIBRETTO-531 trial.

The Solution

By combining concept exploration with instrument testing, we helped:

• Clarify how patients differentiate between levels of side-effect burden
• Identify which response options signal meaningful clinical thresholds
• Validate that the GP5 item is understandable, relevant, and aligned with patient experience

THE OUTCOME

The research confirmed that:

• Side-effect bother is central to how patients define tolerability
• Patients clearly distinguish between response options on the GP5 scale
• Ratings of 3 or 4 reflect high side-effect burden and were linked to high side-effect bother
• The FACT-GP5 item is a fit-for-purpose measure for treatment tolerability in MTC

These insights support stronger, more patient-centered endpoints in clinical trials.