Toward Incorporating Health-Related Quality of Life as Coprimary End Points in Clinical Trials: Time to Achieve Clinical Important Differences and QoL Profiles

PURPOSE Besides morbidity and mortality, quality of life (QoL) is a key outcome of cancer treatments. Trials on the basis of clinical outcomes have expectations that QoL outcomes can be either tolerated or improved. Simultaneously considering QoL and clinical outcomes is challenging with lack of suitable metrics allowing incorporation of QoL as coprimary end points in clinical trial design and utilization of hierarchical hypothesis testing. METHOD We propose combining time to achieving a minimal clinically important difference (MCID) and probabilities of a MCID occurring in each QoL domain to provide QoL metrics analogous to those used for clinical end points. For QoL domains of interest, these yield QoL profiles, time to MCID, and number needed to treat. Incorporation of QoL as coprimary end points in clinical trial designs through hierarchical hypothesis testing can easily be achieved. The noninferiority designed Laparoscopic Approach to Carcinoma of the Endometrium trial, evaluating laparoscopic versus open abdominal surgery for endometrial cancer with Functional Assessment of Cancer Therapy–General QoL domains, is used to illustrate the usefulness of these metrics. RESULTS This analysis revealed that laparoscopic surgery had a significant shorter time to MCID for physical and functional well-being QoL domains (physical mean: 1.5 months, 95% CI, 0.5 to 2.6; P = .002; and functional mean: 1.4 months; 95% CI, 0.4 to 2.4; P = .003) than abdominal surgery, but little difference between the two approaches for psychologic social and emotion well-being. Probability profile plots show a consistent > 2-fold higher chance of attaining a MCID for physical and functional well-being over time for laparoscopic compared with abdominal surgery. CONCLUSION This analysis reinforces the potential value of novel MCID metrics and their usefulness in raising the profile of QoL outcomes to complement clinical end points. The methods will allow health professionals to counsel patients about QoL outcomes and clinical outcomes simultaneously.