Abstract
Lung metastases are a common site of spread for many malignant tumours. Pulmonary metastasectomy has been practiced for many years for sarcomas and is now becoming increasingly frequently advocated for patients with many other tumours, especially colorectal cancer. In this article we argue that this procedure is one framed by therapeutic opportunity and not supported by strong evidence. It is potentially harmful and may not be effective. Our argument is based on several important issues: (I) the vagueness of the concept of "oligometastases" and its biological implausibility; (II) the flaws in the often-cited observational evidence, especially selection bias; (III) the lack of any reliable randomised trial evidence of improved survival but evidence of harm; (IV) the failure of strategies to detect metastases earlier to influence overall survival. The introduction of stereotactic radiotherapy and image-guided thermal ablation have made the urge to treat lung metastases stronger but without any good evidence to justify their use. We acknowledge the problems of carrying out randomised trials when there is a clear lack of equipoise in the clinical teams involved but believe that there is an ethical need to do so. Many patients are probably being given false hope of cure or prolonged survival but are at risk of harm from pulmonary metastasectomy or ablation. It is possible that a few patients may benefit but without better evidence we do not know which, if any, do.