The reasons for its rise in incidence lie in a longer lived population, an increased exposure to cancer-causing agents, and advances in diagnostic techniques, which are detecting cancer in deaths that once were attributed to unknown causes.
癌症死亡人數增加的原因，在於診斷技術進步、平均壽命增長和致癌物質增多。也就是說，因為疾病診斷水準提高，使得癌的正確診斷率跟著提高；相對地，以往被視為不明的死因也隨之減少。另方面，癌症是組織器官老化或中老年人的主要毛病，它的增多，也顯示我國人口平均壽命提高了。