Editorial: Therapy-induced metastasis.

The idea for this Special Issue originated from our recent review in Nature Reviews Clinical Oncology entitled "Does the mobilization of circulating tumour cells during cancer therapy cause metastasis?" Martin et al. (Nat Rev Clin Oncol 14:32-44, 2017). While preparing this review, it became evident that an overwhelming number of preclinical and clinical papers were implicating the involvement of all the major and indispensable cancer treatment modalities in causing increased numbers of tumour cells in circulation (CTCs), and potentially increased risk of distant metastasis. This led to our decision to expand the topic by addressing some of the issues associated with therapy-induced tumour progression. Here, we present papers from ten research groups who give a comprehensive coverage of the biological processes and clinical procedures that can lead to enhanced metastasis and/or tumour recurrence. Our authors provide evidence that all the common therapies, including radiotherapy, chemotherapy, fine needle biopsies, surgical procedures and anaesthesia have the potential to contribute to tumour progression.