Decision making in publicly funded healthcare systems must rely on patient-relevant outcomes that directly measure clinical benefit, such as overall survival and quality of life (QoL). However, studies that support market authorization of oncology drugs usually assess surrogate outcomes, without having previously demonstrated that these intermediate outcomes reliably predict clinical outcomes. As part of an HTA process, we evaluated the clinical benefit of osimertinib, compared with platinum-pemetrexed combination chemotherapy, in patients with epidermal growth factor receptor (EGFR) T790M mutation-positive advanced non-small cell lung cancer (NSCLC) that has progressed after first-line EGFR tyrosine kinase inhibitor (TKI) therapy.

We conducted a systematic search of the PubMed database for randomized controlled trials (RCT) published from inception to January 2019. The clinical outcomes of interest were overall survival and QoL. Where trials reported surrogate outcomes, we conducted additional PubMed searches for evidence of validity for predicting clinical outcomes and used guidance on surrogate outcome validation in oncology from the Institute for Quality and Efficiency in Health Care.

Evidence on osimertinib, compared with chemotherapy, for patients with T790M-positive advanced NSCLC that has progressed after EGFR-TKI therapy was obtained from the AURA3 trial. In this study, overall survival data were immature and the results for QoL and symptom domains were not clinically meaningful. In addition, median progression-free survival (PFS) was six months longer for osimertinib than for chemotherapy. However, to date, no study has demonstrated that PFS reliably predicts longer survival or better QoL.

Our HTA suggested that, unless proven, PFS should not be used as a valid surrogate outcome for decision making in public health. For example, the results of the AURA3 trial showed that osimertinib has an effect on the surrogate outcome of PFS in patients with EGFR T790M-positive advanced NSCLC that has progressed after first-line EGFR-TKI therapy, but not on the clinically relevant outcomes of overall survival and QoL. Furthermore, currently available evidence has failed to prove that PFS reliably predicts outcomes that are clinically relevant. Despite this, osimertinib has been given marketing authorization and is widely recommended in clinical guidelines.