Wang J, Dong J, Hechmati G, Maglinte GA, Rong A, Barber BL, Douillard JY. Quality-adjusted survival in patients with RAS wild-type (WT) metastatic colorectal cancer (mCRC) receiving first-line therapy with panitumumab plus FOLFOX versus FOLXFOX alone in the PRIME trial. Poster presented at the American Society of Clinical Oncology Gastrointestinal Symposium; January 15, 2015. San Francisco, CA.

Background: The pivotal phase III PRIME trial demonstrated that, compared with FOLFOX alone, panitumumab plus FOLFOX prolongs overall survival and progression-free survival in patients with RASWT mCRC without having a detrimental effect on overall quality of life. The objective of this analysis was to use the quality-adjusted time without symptoms of disease or toxicity of treatment (Q-TWiST) method to compare quality-adjusted survival between the treatment arms of PRIME.

Methods: Patients with RASWT mCRC from each treatment arm of PRIME were included in this analysis, and the area under the survival curve (AUSC) was estimated using the nonparametric Kaplan-Meier method (48 months follow-up). The AUSC was partitioned into three health states: toxicity (TOX), time without symptoms of disease progression or toxicity (TWiST, i.e., PFS minus TOX), and relapse (REL, i.e., OS minus PFS). The durations of the health states were then adjusted using utility weights derived from patient-reported EuroQoL 5 measures. The null hypothesis of no difference between treatment arms was tested based on the normal approximation, with standard errors calculated by the bootstrap method. In the primary analysis, TOX consisted of grade 3 and 4 adverse events. A sensitivity analysis, with grade 2, 3, and 4 adverse events classified as TOX, was performed.

Results: Of 1,183 patients with mCRC who were randomized, 512 patients had RAS WT tumors (panitumumab plus FOLFOX, n=259; FOLFOX alone, n=253) and were included in this analysis. Patients receiving panitumumab plus FOLFOX had a significantly longer Q-TWiST (20.5 months) than patients receiving FOLFOX alone (18.2 months) resulting in 2.3 ± 1.0 (SE) additional quality-adjusted months (p less than 0.03). The sensitivity analysis yielded similar results, indicating that the analysis was robust.

Conclusions: This Q-TWiST analysis showed that in a previously untreated RAS WT mCRC population, patients treated with panitumumab plus FOLFOX had a significantly improved duration of quality-adjusted survival compared with patients treated with FOLFOX alone. Clinical trial information: NCT00364013 

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