QUASAR
After apparently curative resection of colorectal cancer, does adjuvant fluoropyrimidine chemotherapy improve outcomes compared with observation?
Reported outcome visualization
Key results
The trial estimated an absolute 5-year survival benefit of 3.6 percentage points (95% CI approximately 1.0–6.0) assuming 20% 5-year mortality without chemotherapy; recurrence was also reduced.
Absolute Effect
Estimated NNT ≈28 for one additional survivor at 5 years (1/0.036), conditional on the trial's stated baseline-risk assumption. The absolute gain varies with baseline recurrence risk.
NNT: ≈28, based on 5-year overall survival under the trial's stated baseline-risk assumption.
NNH: Not quantifiable from the verified fixed-time toxicity data used in this summary; see toxicity and treatment burden below.
Time-to-event interpretation: Hazard ratios and median survival are relative/time-to-event measures; they are not converted into NNT unless a fixed-time absolute event estimate is available.
Toxicity and treatment burden
Fluoropyrimidines can cause diarrhoea, mucositis, cytopenias and rare severe toxicity including cardiotoxicity; DPD deficiency is a critical modern safety consideration. NNH is not calculated without a comparable prespecified fixed-time toxicity endpoint.
Follow-up, limitations and maturity
Follow-up: Median follow-up approximately 5.5 years.
Mixed colorectal population and historical fluorouracil regimens; the absolute benefit is small and depends on baseline risk. The trial does not imply that every stage II patient should receive chemotherapy.
Clinical interpretation
Adjuvant fluoropyrimidine offers a small average survival gain after resection; decisions in stage II disease should be risk-adapted rather than based on relative effect alone.
Primary publication and sources
QUASAR Collaborative Group. Lancet. 2007;370:2020–2029.
Current-practice context · reviewed 15 October 2026
QUASAR's small estimated average survival gain should not lead to routine chemotherapy for all stage II colon cancer. Current risk-adapted decisions consider T4 disease, inadequate nodal sampling, lymphovascular/perineural invasion, obstruction/perforation, tumour budding and mismatch-repair/microsatellite-instability status. Fluoropyrimidine monotherapy is not routinely recommended for dMMR/MSI-H stage II tumours.
ASCO guideline update: adjuvant therapy for stage II colon cancer ↗