Incomplete uptake of EGFR mutation testing and its impact on estimation of mutation prevalence in patients with non-squamous NSCLC: A population-based study in New Zealand.

Background: Epidermal Growth Factor Receptor (EGFR) mutation testing is recommended for patients with non-squamous non-small cell lung cancer (NSCLC) but not all eligible patients get tested, which may bias the mutation prevalence estimated. This study aims to examine trends in the uptake of EGFR mutation testing in patients with non-squamous NSCLC in New Zealand; to develop a composite metric that quantifies the influences of demographic and clinico-pathological factors on the testing uptake; and to estimate the prevalence of EGFR mutation if all patients were tested.

Methods: This population-based study involved all patients who were diagnosed with non-squamous NSCLC in four health regions in New Zealand between January 2010 and December 2015. Eligible patients were identified from the New Zealand Cancer Registry and information on EGFR mutation testing was obtained through linkage to TestSafe, a clinical information sharing service, and laboratory records.

Results: Of 2701 eligible patients, 1059 (39.2%) were tested for EGFR mutation. The testing prevalence increased (3.7% in 2010 to 64.6% in 2014) and the influences of demographic and clinic-pathological factors decreased from 2010 to June 2014, and remained stable afterward. Of the tested patients, 229 (21.6%) were mutation positive with a decreasing trend observed from 2010 (43.8%) to June 2014 (16.8%). The best-fit log-linear model estimated the prevalence of EGFR mutation, if all patients were tested, as 15.5% (95% CI: 13.2%-18.0%).

Conclusion: The methods described here allowed a more accurate estimation of the prevalence of EGFR mutation.