Scientists search the microbiome for clues to the rise in colorectal cancers

Unlike many cancers, colorectal cancer has become more lethal for people at younger ages. Doctors are sleuthing out why. JUANA SUMMERS, HOST: Science has made many cancers more treatable and survivable, but colorectal cancer has become more lethal for people at younger ages. NPR's Yuki Noguchi reports doctors have been trying to find out why. YUKI NOGUCHI, BYLINE: Like so many in her field, Ohio State University oncologist Ning Jin is alarmed by the number of patients in their 30s and 40s with late-stage cancer in their lower digestive tract. It's not just that these patients are decades younger than what had been typical for colorectal cancer. Jin says the tumors themselves are also more stubborn to treat. NING JIN: Even though we treat young patients more aggressive by chemo, more chemo or more surgery, patients' outcome is not necessarily better. NOGUCHI: Jin says about a fifth of patients have hereditary markers that increase risk of these cancers. But that doesn't explain the remaining 80% of cases. JIN: So there must be some environmental factor or changes. NOGUCHI: Figuring out what's causing more cancers among younger patients is a huge medical mystery. And while detection and treatment are both improving, this rising incidence is undermining that progress, especially when it comes to colorectal cancer. Veteran oncologist John Marshall runs the Lombardi Cancer Center at Georgetown University. …