Quality-Adjusted survival with combination nab-paclitaxel+gemcitabine vs gemcitabine alone in metastatic pancreatic cancer: A Q-TWiST analysis

Abstract

Objectives: To use the Quality-Adjusted Time Without Symptoms or Toxicities (Q-TWiST) methodology to compare the quality-of-life and survival benefits associated with the combination of albumin-bound (nab)-paclitaxel and gemcitabine vs gemcitabine alone in the first-line treatment of metastatic pancreatic adenocarcinoma. Methods: Total survival time through 45 months was partitioned into time before disease progression without toxicity grade °3 (TWiST), time with adverse event grade °3 (TOX), and time of disease progression (REL). Mean Q-TWiST was calculated by multiplying time spent in each health state by its respective utility (i.e., TWiST=1.00; TOX/REL=0.50, 0-1 in sensitivity analyses). Non-parametric bootstrap 95% confidence intervals (CI) were derived to assess the significance of between-treatment differences in TOX, TWiST, REL, and Q-TWiST. A relative gain in Q-TWiST (vs mean overall survival of gemcitabine) of °10% and °15% was defined as clinically important and clearly clinically important, respectively. Results: Patients on nab-paclitaxel+gemcitabine spent a significantly longer time in every state and experienced significantly greater overall Q-TWiST (+1.7 months [95% CI=0.8, 2.7]) than those receiving gemcitabine alone (8.2 months [95% CI=7.5, 8.9] vs 6.5 months [95% CI=5.8, 7.0]), assuming base-case utilities of TOX/REL=0.50. This Q-TWiST gain ranged from 1.0 month (95% CI=0.1, 1.9), when REL/TOX utilities were both 0, to 2.5 months (95% CI=1.3, 3.7), when REL/TOX utilities were both 1. Relative gains in Q-TWiST were 21% in favor of nab- paclitaxel+gemcitabine in the base case, and ranged from 12-30% in sensitivity analyses. Conclusions: There are limitations to Q-TWiST analyses, e.g., imprecision when defining duration/severity of TOX and lack of prospective collection of utilities. This analysis addressed these issues via sensitivity analyses and conservative assumptions to show that nab-paclitaxel+gemcitabine results in statistically significant and clinically important gains in quality-Adjusted survival, when compared to gemcitabine alone, in treatment-naive metastatic pancreatic adenocarcinoma patients. © 2014 Informa UK Ltd.