Abstract: Methods of identifying subjects at increased risk of cancer, based upon detection of biofilms and/or biofilm-associated microbes within a subject, are disclosed. Therapies designed to prevent formation and/or reduce the size of biofilms in a subject identified to be at increased risk of cancer based upon detection of biofilms and/or biofilm-associated microbes are disclosed. In particular embodiments, the invention provides for identification of a subject at elevated risk of developing or having colorectal cancer and/or a colorectal adenoma, based upon detection of a biofilm and/or biofilm-associated bacteria within the gastrointestinal tract of the subject (optionally, within a biopsy specimen and/or stool sample of such subject). Therapies involving administration of an antibiotic agent and/or a probiotic agent to a subject, to prevent or reduce biofilm formation within the gastrointestinal tract of the subject, optionally provided in combination with additional cancer therapy, are also disclosed.