In the end, the study's most compelling take home message, and one that the authors themselves do stress, is that 40 percent of cancers are in fact preventable. Many would argue the percentage is actually higher based on other reports and lines of evidence. Regardless, 40 percent is a large number—and represents millions of lives worldwide that could be saved by investing more in prevention research. Silent Spring Institute. 
[See the most recent study as included previously: Stem cell divisions, somatic mutations, cancer etiology, and cancer prevention]