Quality-of-life-adjusted survival for comparing cancer treatments. A commentary on TWiST and Q-TWiST.

In chronic disease situations where treatment comparisons favor no particular therapy, or where definitive outcome requires a considerable follow-up period, it is useful to have additional and perhaps intermediate endpoints of relevant clinical significance to compare treatments. One such endpoint is Time Without Symptoms and Toxicity (TWiST) which, together with Q-TWiST, attempts to address the quality of life of patients receiving the competing regimens. This paper provides a commentary on these techniques with an emphasis on the problems inherent in implementing Q-TWiST, a measure that attempts to incorporate patient value preferences into TWiST. It is argued that while Q-TWiST is intuitively appealing in the clinical setting, there are formidable design and psychometric hurdles that must be overcome to fully operationalize the concept.