title: Interventional oncology research in the United States: slowing growth, limited focus, and a low level of funding.
abstract: OBJECTIVE
  To establish the characteristics of published interventional oncology (IO) research, including the volume, growth, geographic distribution, type of research, and funding patterns, and to determine how IO research compares with overall radiology research.
  
  
  METHODS
  This retrospective bibliometric analysis of public data was exempt from Institutional Review Board approval. IO articles published between 1996 and 2008 were identified in the National Library of Medicine MEDLINE database. Country of origin, article methodology, study topic, and source of funding were recorded. Growth was analyzed by using linear and nonlinear regression.
  
  
  RESULTS
  Total journal articles numbered 3801, including 847 (22.3%) from the United States, 722 (19.0%) from Japan, and 390 (10.3%) from China. World publications grew with a sigmoid (logistic) pattern (predicted maximum of 586.8 articles per year, P < .001). The United States and China also had logistic and slowing growth (maximums of 111.0 and 48.1 articles per year, respectively; both P < .001). Growth was linear in Japan (growth of 3.0 articles per year, P < .001) and exponential and accelerating in Germany, Italy, South Korea, France, and the United Kingdom. The United States produced 187 (36.9%) review articles but only 52 (13.1%) clinical trials. Japan (75, 18.8%) and China (71, 17.8%) both produced more clinical trials than other countries. U.S. IO articles were less likely than general radiology articles to receive funding from government (12.5% vs 23.7%) and nongovernment (15.0% vs 17.0%) sources. Liver cancer articles constituted 2388 (62.8%) of all IO articles.
  
  
  CONCLUSIONS
  IO research is slowing in the United States but growing elsewhere. Japan and China are leaders in clinical trial research. U.S. IO research receives less funding than does overall radiology research. IO research focuses primarily on liver cancer.
authors.affiliation: Department of Radiological Sciences, University of California Los Angeles, Los Angeles, CA, USA.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Chow
authors.forename: Michael W
authors.initials: MW
authors.lastname: Itagaki
mesh_terms: D015706:Bibliometrics; D035843:Biomedical Research / Q000191:economics / Q000639:trends; D002681:China; D005544:Forecasting; D006801:Humans; D007564:Japan; D008495:Medical Oncology / Q000191:economics / Q000639:trends; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000628:therapy*; D011642:Publications / Q000706:statistics & numerical data; D015641:Radiography, Interventional / Q000191:economics / Q000639:trends; D012044:Regression Analysis; D012109:Research Support as Topic / Q000191:economics; D012189:Retrospective Studies; D014481:United States