As an adjective cancerogenic is carcinogenic.
As a noun carcinogen is a substance or agent that can cause cancer.
As an adjective cancerogenic is carcinogenic.
As a noun carcinogen is a substance or agent that can cause cancer.
As nouns the difference between cancer and carcinogen is that cancer is (medicine|oncology|disease) a disease in which the cells of a tissue undergo uncontrolled (and often rapid) proliferation while carcinogen is a substance or agent that can cause cancer.