Nature and AACR track unexplained surge of colorectal, uterine, liver and breast cancer under 50

Researchers from *Nature* and the American Association for Cancer Research (AACR) highlighted a rapid increase in colorectal, uterine, liver, and breast cancers among adults under 50 worldwide. Presentations from the AACR’s April meeting in San Diego and the American Society of Clinical Oncology (ASCO) meeting in Chicago revealed that over 9,000 cancer cases are diagnosed daily in this age group globally. In the U.S., advanced colorectal cancer cases among 20–49-year-olds have risen by about 3% annually since 2010, surpassing other cancers as the leading cause of cancer death in that group in 2023. The study suggests early-life exposures may drive the surge. Ludmil Alexandrov, from the University of California, San Diego, found colibactin—a toxin produced by gut bacteria—causes mutations in colorectal cancer patients under 40 at rates 3.3 times higher than in those aged 70 or older. His research, published in *Nature* last April, showed these mutations appear as early as age 5, with 25% of APC gene mutations linked to colibactin. At this year’s AACR meeting, Alexandrov warned that children under 2 may already carry mutation burdens comparable to middle-aged adults. Maternal obesity during pregnancy is another potential factor. Andrew Chan, a physician at Massachusetts General Hospital, noted that greater maternal weight gain correlates with higher offspring colorectal cancer risk, suggesting fetal development plays a role. However, Kimmie Ng, director of the Young-Onset Colorectal Cancer Center at Dana-Farber Cancer Institute, emphasized that obesity alone doesn’t explain all cases. She cited a *Nature Medicine* study using DNA epigenetic marks to identify additional risk factors, stressing the need for further research. Sun Hee Y. Choi of the American Cancer Society cautioned that current trends may foreshadow a larger crisis as this generation ages. While cancer deaths under 50 remain a small share of total mortality, the rising incidence raises concerns about long-term health impacts. Researchers are now focusing on preventing early colibactin exposure and identifying other environmental triggers to curb the growing burden of young-onset cancers.