Fig. 4. Diagrams and graphs show the quantitative proportions and trends of published articles by cancer type. (A) Breast cancer was the most studied cancer type. The total was 54,556, accounting for 37%. Followed by gastric cancer at 24,290 (17%) and colorectal cancer 22,251 at 15%. In order, 15,573 (11%) of lung cancer, 10,932 (7%) of prostate cancer, 5,235 (4%) of esophagus cancer, 4,998 (3%) of gynecologic cancer and 3,975 (3%) of pancreatic cancer. (B) It shows trends by cancer type. Breast cancer has been the most abundant since 1980 and has steadily increased to the present, followed by stomach cancer, colorectal cancer, and lung cancer. (C) A graph that standardizes the amount of published journals to normalized frequency. According to this, breast cancer increased steadily to a normalized frequency of 0.38 until 2002, but then slowly increased to 0.39 by 2017. Gastric cancer, colorectal cancer, and lung cancer have slowly increased until now.