Two-thirds of cancers in adults can be attributed to random mutations in genes.

A Johns Hopkins Medicine study found they’re capable of triggering the growth of many cancers, including brain, pancreatic, testicular and ovarian along with leukemia.

Researchers say bad habits and heredity appear to play a larger role in colorectal, lung and skin cancers.

Breast and prostate cancers were not included in the study because researchers say those diseases are simply too complex.

They say the landmark study, which appears in the journal Science, makes a strong case for early detection.