This is the first time that researchers have “provided unbiased estimates of the number of mutations” that are needed for cancer to emerge. Their findings — which have been published in the journal Cell — also reveal that the number of mutations required to drive cancer significantly varies depending on the type of cancer.

The study was conducted by lead author Dr. Peter Campbell, first author Dr. Iñigo Martincorena, and co-author Prof. Michael Stratton, all of whom are from the Wellcome Trust Sanger Institute in the United Kingdom.

“We have addressed a long-standing question in cancer research that has been debated since the 1950s: how many mutations are needed for a normal cell to turn into a cancer cell?” says Dr. Campbell.

“The answer is,” he adds, “a small handful. For example, about four mutations per patient on average drive liver cancers, whereas colorectal cancers typically require 10 or so driver mutations.”

The Wellcome Trust Sanger Institute and collaborators identified a strategy to distinguish the genes that are involved in cancer evolution and the number of mutations in those genes that play a role in causing cancer. This approach could be used in the future to help clinics identify the few mutations, among thousands, that are driving cancer in an individual patient.

Charles Darwin described, more than 150 years ago, how various species evolve through natural selection. Cancer similarly occurs by the natural selection process, acting on the mutations that develop in our bodies’ cells over time.

More cancer genes yet to be discovered

The researchers applied an evolutionary perspective to quantify the process of natural selection in their analysis of 7,664 tumors across 29 cancer types. The team cataloged the primary cancer genes involved in 29 types of cancer.

Furthermore, they discovered new genes associated with cancer and attempted to clarify the completeness of the current lists of cancer genes.