Quality-adjusted survival (Q-TWiST) analysis of EORTC trial 30853: Comparing goserelin acetate and flutamide with bilateral orchiectomy in patients with metastatic prostate cancer

BACKGROUND. The first data analysis of the European Organization for Resear ch and Treatment of Cancer (EORTC) 30853 trial indicated a significantly lo nger time to progression and duration of survival for the maximal androgen blockade (MAB) treatment arm. However, the MAB treatment arm had a higher f requency of reported side effects. METHODS. The quality-adjusted survival (Q-TWiST) method was applied to perf orm a secondary analysis of the EORTC 30853 trial in order to obtain a qual ity-adjusted survival (QAS) analysis. Two models with different definitions of the progression health state were used for the analysis. In the first m odel, progression was defined by both objective and subjective criteria, an d in the second model only by increase in pain score. The approach was also extended to include an analysis using actual utility scores (Q-tility) of patients in the relevant health states. RESULTS. Based on Q-tility scores obtained from a separate study of a cohor t of prostate cancer patients, the QAS analysis resulted in a 5.2-month dif ference (95% CI, -1.1; 11.5 months) in favor of zoladex and flutamide, equa l in magnitude to the benefit found in the unadjusted survival analysis. CONCLUSIONS. A QAS analysis such as the Q-TWiST method may be preferred ove r the unadjusted approach in clinical trials where the health states are cl early distinct, and differ significantly in either duration or quality of l ife (QOL), or both. The second model, with progression defined as increase in pain score, made no difference to the results in this study because of t he small difference in duration of the pain-progression health state betwee n treatment arms. However, Q-tility scores from the separate cross-sectiona l study that was used in this Q-TWiST analysis showed that a subjective def inition of health states better reflects differences in QOL between the hea lth states that the patients experience during follow-up. (C) 1999 Wiley-Li ss, Inc.