MSFinals-0697

A 68-year-old man presents to the General Surgical Outpatient Clinic with a 4-week history of altered bowel habit. There is no history of rectal bleeding, although faecal occult blood testing is positive. He denies any other symptoms from the abdominal point of view, and his general examination is otherwise unremarkable.
You discuss this case with the patient and agree that the next best step would be to undergo a colonoscopy and some blood tests. The results are shown below:
Bloods:
Investigation Result Normal value
Haemoglobin 112g/l 135–175 g/l
White cell count (WCC) 7.2 × 109/l 4–11 × 109/l
Platelets 205 × 109/l 150–400 × 109/l
Urea 4.5 mmol/l 2.5–6.5 mmol/l
Creatinine 71 mmol/l 50–120 μmol/l
Sodium (Na+) 135 mmol/l 135–145 mmol/l
Potassium (K+) 4.1 mmol/l 3.5–5.0 mmol/l
Endoscopy Report:
The endoscope was passed to the caecum without complication. The caecum was identified with confidence as the ileocaecal valve and appendicular orifice were seen and also confirmed with transillumination. There are multiple diverticulae seen in the sigmoid colon. A large ulcerated and haemorrhagic lesion resembling a tumour was found at the splenic flexure. Multiple biopsies were taken and sent for histology. Small polyp found in ascending colon, snared without complication.
Follow-up with histology results in General Surgery Clinic in one week. Histology to be discussed at the next gastrointestinal multidisciplinary meeting.
The histology results come back as adenocarcinoma of the colon involving the splenic flexure. Further staging reveals no initial metastatic disease.
Which of the following is the next best course of action?