Fatigue in Advanced Cancer Patients: Congruence Between Patients and Their Informal Caregivers About Patients' Fatigue Severity During Cancer Treatment With Palliative Intent and Predictors of Agreement.

Context: Informal caregivers (ICs) are increasingly involved in the monitoring of symptoms during advanced cancer patients' treatment with palliative intent. A common but subjective symptom during this extended treatment phase is fatigue.

Objectives: This exploratory longitudinal study aimed to determine agreement between patients and ICs about patients' fatigue severity. In addition, predictors of agreement over time were studied.

Methods: A sample of 107 patients with advanced cancer (life expectancy ≥ six months) and their ICs completed the subscale fatigue severity of the Checklist Individual Strength based on the patient's status at baseline and six months later. This eight-item subscale has a validated cutoff to determine the presence of clinically relevant levels of fatigue. ICs' own fatigue severity, strain, self-esteem, and relationship satisfaction were examined as predictors of agreement.

Results: A total of 107 dyads completed measures at baseline and 69 dyads six months later. At baseline, ICs' significantly overestimated patients' fatigue severity (P < 0.001) with a moderate amount of bias (Cohen's d = 0.48). In 81 of the 107 dyads (76%), there was congruence about the presence or absence of severe fatigue. On a group level, congruence did not significantly change over time. On a dyad level, there was a tendency to either remain congruent or reach congruence. Next to baseline congruence, ICs' fatigue severity and strain predicted ICs' fatigue ratings (R(2) = 0.22).

Conclusion: Most ICs accurately predict presence or absence of clinically relevant levels of patients' fatigue. ICs' own fatigue severity and strain should be taken into account as they influence agreement.