A lung cancer molecular prognostic test ready for prime time.

Lung cancers with different prognoses should have different biological properties, which in turn should be reflected in different gene expression profiles. In the best of all scenarios, these differentially expressed genes would also be functionally relevant and potential therapeutic targets. If such tumours could be identified when patients have only microscopic disease, curative treatment should be most effective. Yet in practice this approach has been very challenging—many studies have yielded prognostic signatures, but these seldom overlap with other signatures. Prognostic signatures are usually tested and validated in small samples, with methods that might not be transferable to real-life clinical situations. Thus, the report by Johannes Kratz and colleagues5 in The Lancet is important, providing a lung cancer molecular prognostic signature that seems ready for widespread use.