Q-TWiST analysis of ixabepilone in combination with capecitabine on quality of life in patients with metastatic breast cancer

BACKGROUND: Combination therapy with ixabepilone and capecitabine (cape) is approved for use in patients with locally advanced/metastatic breast cancer that is resistant to treatment with anthracyclines or taxanes. The current study evaluated the trade-off between quality and quantity of life using quality-adjusted time without symptoms or toxicity (Q-TWiST) outcomes. METHODS: Within the trial, 752 women were randomly assigned to receive either the combination of ixabepilone and cape (once every 21 days) or cape alone (on days 1- 14). The area under the survival curve was partitioned into 3 health states: toxicity (TOX), time without symptoms of disease progression or toxicity, and recurrence (relapse [REL]). The mean time in each health state was weighted by a range of utilities and summed to estimate quality-adjusted survival (QAS). Patient-reported outcomes were also evaluated using the Functional Assessment of Cancer Therapy (FACT)-Breast Symptom Index (FBSI). RESULTS: A statistically significant difference between groups with regard to change from baseline FBSI scores favoring the cape group was observed (P.0002), but no differences were observed after adjusting for deaths in the analysis. All combinations of utilities for REL and TOX resulted in an observed difference in QAS favoring combination therapy. Differences were found to be statistically significant for comparisons, with higher tolerance for TOX. QAS was found to be greater for the combination therapy group (42.2 weeks vs 38.4 weeks), assuming the base case scenario of utility equal to 0.5 for both TOX and REL (P=.0227). CONCLUSIONS: The Q-TWiST analysis supports a positive benefit-risk ratio for the combination of ixabepilone plus cape in patients with advanced/metastatic breast cancer that is refractory to anthracyclines and taxanes versus cape alone, despite the potential for added toxicities with combination therapy. Cancer 2012; 118: 461-8. (C) 2011 American Cancer Society.