1. Literature search

We systematically searched through the databases (Cochrane Central Register of Controlled Trials, Embase, EBSCO, Ovid, PubMed, Science Direct and Wiley Online Library, China National Knowledge Infrastructure (CNKI) and Wan Fang database) to obtain relevant articles that were published before 1 January 2020. The following terms and phrases were used as search criteria: ‘circadian clock gene’ or ‘period1 (Per1)’ or ‘period2 (Per2)’, or ‘period3 (Per3)’ or ‘cryptochrome1 (Cry1)’ or ‘cryptochrome2 (Cry2)’ or ‘aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1)’ or ‘neuronal PAS domain protein 2 (Npas2) ’ or ‘circadian locomoter output cycles protein kaput (CLOCK)’ and ‘neoplasm’ or ‘tumor’ or ‘cancer’, ‘carcinoma’ and ‘prognosis’ or ‘overall survival (OS)’ or ‘mortality’ or ‘clinic outcome’ or ‘clinicopathological feature’ or ‘odd ratio (OR)’ or ‘hazard ratio (HR)’. The title and abstract of each study obtained in the search was scanned to exclude any clearly irrelevant ones. The remaining articles were reviewed, analyzed, evaluated to determine whether they contained information on the topic of interest. The reference lists of these articles with information on the topic were also reviewed for additional pertinent studies.