Summary

The new capability to generate mimicking chemical analogues and perform mass screenings of candidate drugs has been tested on B-cell receptor signalling, a driver of B-cell malignancies. These efforts have identified ibrutinib as a potent inhibitor of Bruton's tyrosine kinase. As the clinical use of ibrutinib increases, continued vigilant monitoring for rare adverse events is prudent, including the development of secondary malignancies. To date, the most common reported secondary malignancy is non-melanoma skin cancer; however, we present a case of secondary primary lung adenocarcinoma becoming clinically apparent shortly after initiating therapy with ibrutinib. Our patient had a sudden regression of the tumour with discontinuance of ibrutinib, and based on our understanding of paradoxical tumour growth caused by tyrosine kinase inhibitors it is our hypothesis that the complex multikinase activity of ibrutinib may stimulate tumour growth by targeting a subset of protein kinases critical for growth in some cancer cells.