Dear Doctors: My husband and I were shocked when our nephew was diagnosed with colon cancer. Dear Reader: Unfortunately, you’re correct about the increase in the number of younger adults being diagnosed with colon cancer at this time. Until recently, colon cancer was not prevalent among younger adults. Others worry that younger adults are ignoring the physical symptoms that may indicate the presence of colorectal cancer. The good news is that, when caught early, colorectal cancers are highly treatable.