EvidenceColon cancer (adenocarcinoma of the colon)

An effect size comparable to adjuvant chemotherapy, from a behavioural intervention with no drug cost, which makes the delivery problem (who funds the trainers) the binding constraint rather than the evidence.

The predictive half of the ctDNA case: chemotherapy after surgery helps the patients whose blood test is positive and appears to do little for those whose test is negative, which is the rationale for the randomised CIRCULATE trials now running in Japan, the United States and Europe.

A UK-led trial that moved part of colon cancer chemotherapy in front of the operation, and showed that tumour regression grade after six weeks predicts recurrence, which is the basis for using the response itself to choose what follows.

De-escalation guided by a blood test is now proven in stage II colon cancer, and is the template for the stage III and rectal trials that follow; the unsolved half is what to do for the positives, whose recurrence-free survival remains the worst in the trial even after chemotherapy.

Chemoprevention in a defined high-risk group is possible, and aspirin is now offered to Lynch syndrome carriers in UK practice; the CaPP3 dose-finding study asks whether a much smaller dose does the same.

The European rulebook for what happens after a colon cancer operation, and the reason a patient with a T3 N1 tumour is now offered three months of chemotherapy rather than six.

The largest de-escalation exercise in adjuvant oncology, and the reason a patient with a T3 N1 colon cancer is now offered four cycles of CAPOX rather than twelve of FOLFOX, with a fraction of the neuropathy.

Minimal residual disease became measurable in solid tumours, and the DYNAMIC and CIRCULATE trials that followed turned the measurement into a treatment decision.