A 22-year-old female patient presents to your office with rectal bleeding and family history of colon cancer in her sister who was diagnosed at age 28 years. Esophagogastroduodenoscopy demonstrates three gastric and duodenal adenomas. Colonoscopy demonstrates hundreds of polyps throughout her colon. Pathology demonstrates tubular adenomas. You perform a flexible sigmoidoscopy that confirms nine polyps in her rectum; the polyps range from 4 mm to 9 mm in size. She is interested in having children in the near future. What is the recommended next step in her management?