On the basis of these values, the between-group Q-TWiST difference was 6.1 weeks (P=0.006, Table 1).
The Q-TWiST difference is clinically meaningful and was statistically significant across an entire matrix of possible utility weights.
Based on a combination of trial-based and external utility scores, the Q-TWiST difference in this trial was 0.50 months (P=0.0326) favoring ipilimumab after 1 year.
With 2-year follow-up, the Q-TWiST difference across a matrix of utility values ranged from 0.8 to 2.0 months.
The magnitude of the Q-TWiST difference (in months) is given by the numbered lines within the plot, with positive numbers favoring ipilimumab therapy over placebo.
These results are indicative of the average Q-TWiST difference we would expect among patients with this disease taking these treatments.
Based on an analysis of Q-TWiST studies in oncology, it was recommended that a Q-TWiST difference of 10% or more be considered clinically important, with differences of 15% or more being clearly clinically important.
To look specifically at the utilities and the corresponding Q-TWiST difference that would be expected in a group of melanoma patients, we reran the analyses with utility scores from two additional sources.
The corresponding Q-TWiST difference among patients with an age ⩾70 (i.e., 2.0 months, +16.2%) also favoured nab-PC, albeit without statistical significance, perhaps due to smaller number of patients.
Based on this combination of trial-based and external utility scores of 0.67, 0.80 and 0.76 for TOX, TWiST and REL, respectively, the Q-TWiST difference in this trial was 0.50 months (P=0.0326) favoring ipilimumab after 1 year (Table 2).
However, in patients aged ⩾60 years, the Q-TWiST was significantly better for the nab-PC arm when a total follow-up period of ⩾9 months was considered (mean Q-TWiST difference at 9 months, 0.4 months, 95% CI: 0.02 0.8).
