The FACT-GP5 as a global tolerability measure: responsiveness and robustness to missing assessments

Area of Science:

• Oncology
• Clinical Trials
• Patient-Reported Outcomes

Background:

• The Functional Assessment of Cancer Therapy item (FACT-GP5) assesses patient-perceived treatment tolerability.
• Longitudinal evaluation and the impact of missing data (missing-not-at-random) on FACT-GP5 have not been previously explored.
• This study evaluates the robustness of FACT-GP5 to missing data assumptions and its responsiveness to key side effects.

Purpose of the Study:

• To evaluate the longitudinal trajectory of the FACT-GP5 in patients with advanced breast cancer.
• To assess the responsiveness of the FACT-GP5 to key clinical indicators like CTCAE grade and ECOG Performance Status.
• To determine the impact of missing data on the FACT-GP5's validity and reliability.

Main Methods:

• A randomized, double-blind study (NCT00065325) involving 618 postmenopausal women with HR+ advanced breast cancer.
• Patients received either fulvestrant or exemestane and completed FACT measures monthly for seven months.
• Cumulative link mixed models (CLMM) were used to analyze FACT-GP5 trajectory and responsiveness, with sensitivity analyses for missing-at-random (MAR) assumptions.

Main Results:

• Patient-reported side-effect bother increased over time.
• FACT-GP5 demonstrated positive within-person correlations with other FACT items, ECOG performance status, and CTCAE grade.
• Missing FACT-GP5 assessments influenced the trajectory but not the relationships with other items, except for nausea.

Conclusions:

• The FACT-GP5 is a responsive measure for assessing patient-reported treatment tolerability.
• The responsiveness of FACT-GP5 is generally robust to missing data.
• Missing data should be accounted for when interpreting longitudinal changes in FACT-GP5 scores.