Lynch Syndrome-Associated Colorectal Cancer

A 48-year-old man presents with intermittent lower abdominal pain on his right side and reports a weight loss of 4.5 kg (10 lb). He is married and has two healthy teenage children. The physical examination is remarkable for the presence of blood in the stool on digital rectal examination. The hemoglobin level is 11.4 g per deciliter. His mother had a gynecologic cancer at 45 years of age, and his maternal grandfather had colorectal cancer at 63 years of age. Computed tomography of the abdomen and pelvis shows thickening of the cecal wall and pericecal adenopathy. A colonoscopy reveals a polypoid cecal mass, and a biopsy shows poorly differentiated adenocarcinoma. How should this patient be further evaluated and treated?