Rethinking end-points for bone-targeted therapy in advanced cancer

The principal objective for any medical therapy is to improve either the duration of life and/or its quality. Metastases in bone can lead to clinically defined events termed skeletal-related events (SREs) which are a quantifiable measure of skeletal morbidity. Avoidance and/or delay of SREs have become the principal objective in trials exploring the efficacy of bone-targeted therapy in patients with skeletal metastases. Despite reductions in the frequency or rate of SRE occurrence, trials of bone-targeted therapy have failed to show any effect on either progression-free or overall survival when compared with placebo or other bone-targeting agents. Similarly, trials of bone-targeted therapy have not shown consistent effects on quality of life. The validity of SRE-based primary outcome measures in cancer clinical trials is therefore, questionable. More novel end-point selection for trials of bone-targeted therapy seems warranted. Composite measures comprising occurrence of symptomatic skeletal events and patient reported outcomes may be an effective solution and warrants further investigation.