Characteristics and patient-reported outcomes associated with dropout in severely affected oncological patients: an exploratory study

Abstract

Background: Patient-reported outcome measures (PROMs) are commonly-used surrogates for clinical outcomes in cancer research. When researching severe diseases such as cancer, it is difficult to avoid the problem of incomplete questionnaires from drop-outs or missing data from patients who pass away during the observation period. The aim of this exploratory study was to explore patient characteristics and the patient-reported outcomes associated with the time-to-dropout.

Methods: In an Oncological Social Care Project (OSCAR) study, the condition of the participants was assessed four times within 12 months (t0: baseline, t1: 3 months, t2: 6 months, and t3: 12 months) by validated PROMs. We performed competing-risk regressions based on Fine and Gray's proportional sub-distribution hazards model for exploring factors associated with time-to-dropout. Death was considered a competing risk.

Results: Three hundred sixty-two participants were analyzed in the study. 193 (53.3%) completed a follow-up after 12 months, 67 (18.5%) patients dropped out, and 102 patients (28.2%) died during the study period. Poor subjective social support was related to a higher risk of drop-out (SHR = 2.10; 95%CI: 1.01-4.35). Lower values in health-related quality of life were related to drop-out and death. The sub-scales global health status/QoL, role functioning, physical functioning, and fatigue symptom in the EORTC QLQ-C30 were key characteristics of early drop-out.

Conclusion: Severely affected cancer patients with poor social support and poor quality of life seem more likely to drop out of studies than patients with higher levels of social support and a better quality of life. This should be considered when planning studies to assess advanced cancer patients. Methods of close continued monitoring should be actively used when patient experiences a substantial deterioration in their health-related quality of life and symptoms during the study. Results for such studies have to be interpreted with caution in light of specific drop-out mechanisms.

Trial registration: OSCAR study was registered to the German Clinical Trials Register (DRKS-ID: DRKS00013640 ). Registered 29 December 2017.

Keywords: Advanced cancer; Attrition; Cancer; Health-related quality of life; Monotone missing data; Non-compliance; Patient-reported outcome measures.

Fig. 1

Cumulative incidence of all drop-out causes (green solid line) and drop-out with death as a competing risk (orange dotted line)

Fig. 2

Patient-reported outcomes at baseline and at the visit prior to drop out, and their association to time-to-dropout, with death as a competing risk. n = the observation number, SHR = Sub-hazard ratio, CI=Confidence interval, High values of global health status/QoL and functional sub-scales in the EORTC QLQ-C30 indicate a better outcome, High values of symptom sub-scales (e.g fatigue, nausea/vomiting, pain etc.) and DCS indicate a poorer outcome

Fig. 3

Patient-reported outcomes at baseline and at the visit prior to death, and their association to time-to-death. n = the observation number, HR = Hazard ratio, CI=Confidence interval, High values of global health status/QoL and functional sub-scales in the EORTC QLQ-C30 indicate a better outcome, High values of symptom sub-scales (e.g fatigue, nausea/vomiting, pain etc.) and DCS indicate a poorer outcome

Fig. 4

Patterns of patients who (a) dropped out or (b) died: Sub-scales of the EORTC QLQ-C30 versus follow-up times, stratified by time of drop-out or death. The possible range of the EORTC QLQ-C30 is 0–100, with higher values indicating a better QoL in global health status/QoL, physical functioning, role functioning, social functioning, and lower values indicating better symptoms for fatigue and appetite loss