Background Systematic analyses regarding cancer types of patients enrolled in oncology phase I trials are scarce. The global distribution, time-dependent change, and regional differences were evaluated. Methods A systematic search of the PubMed database, in which all single-agent phase I trials permitting the enrollment of all-comer patients with any type of solid tumor published between January 1991 and December 2015 were specified, was performed. Trials expected to enroll specific patient populations were excluded according to predefined criteria. Results Eight hundred and sixty-six eligible trials, which had enrolled 29,112 advanced solid tumor patients, were identified. Colorectal (n = 7510; 25.8%) and lung cancer (n = 3212; 11.0%) were the most prevalent solid tumors, followed by sarcoma (n = 1756; 6.0%), breast cancer (n = 1623; 5.6%), and renal cancer (n = 1589; 5.5%). The proportion of patients with either colorectal or lung cancer tended to decrease over time. The proportion of trials, in which patients with either of these two cancers accounted for ≥50.0% of the total number of patients in each trial, also decreased: 33 of 67 trials (31/67) (46.3%) in 1991-1995, 58/142 (40.8%) in 1996-2000, 59/223 (26.5%) in 2001-2005, 38/189 (20.1%) in 2006-2010, and 41/245 (16.7%) in 2011-2015. Instead, the proportion of patients with various types of cancer increased, leading to diversification of enrolled patients. Conclusions The distribution of cancer types among patients in phase I trials has changed. The comprehensive review of the distribution of solid tumor types could contribute to flexible trial designs and optimal patient recruitment.
Keywords: Cancer; Cancer type; Global trend; Phase I trial.