# Adjuvant chemotherapy versus observation in patients with colorectal cancer: a randomised study (QUASAR)

Source: https://onco.cc/key-papers/paper-quasar-adjuvant-chemotherapy-vs-observation-lancet-2007/  
OnCo record `paper-quasar-adjuvant-chemotherapy-vs-observation-lancet-2007` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The trial that measured how small the benefit of chemotherapy is for node-negative bowel cancer: about 3.6 people in every 100 avoid dying, which is why the decision is a conversation rather than a rule.

## Summary

QUASAR set out to determine the size and duration of any survival benefit from adjuvant chemotherapy in patients at low risk of recurrence, for whom the indication was unclear. After apparently curative resection, 3,239 patients from 150 centres in 19 countries were randomised to fluorouracil and folinic acid or to observation with chemotherapy considered on recurrence; 2,963 (91 percent) had stage II node-negative disease and 2,291 (71 percent) had colon rather than rectal cancer, with a median age of 63. Until 1997 levamisole or placebo was added; after 1997 the chemotherapy arm received fluorouracil and low-dose folinic acid only. The primary outcome was all-cause mortality, analysed by intention to treat.

Treatment efficacy did not differ significantly by tumour site, stage, sex, age or chemotherapy schedule.

## Fields

- Kind: Key paper
- Last checked: 2026-09-24
- Tags: colorectal-evidence
- Journal: The Lancet
- Year: 2007
- DOI: 10.1016/S0140-6736(07)61866-2
- Authors: Quasar Collaborative Group, Gray R, Barnwell J, et al.
- Findings: After a median 5.5 years, 311 deaths on chemotherapy against 370 on observation: relative risk of death 0.82 (95 percent CI 0.70 to 0.95, p=0.008).; 293 recurrences against 359: relative risk 0.78 (0.67 to 0.91, p=0.001).; Assuming 20 percent five-year mortality without chemotherapy, the absolute survival improvement is 3.6 percent (95 percent CI 1.0 to 6.0).; Eight chemotherapy-group and four observation-group patients died of non-colorectal causes within 30 weeks; one death was deemed possibly chemotherapy related.
- What it means: The number every stage II conversation still uses. It is also the baseline against which ctDNA-guided de-escalation is judged: DYNAMIC halved chemotherapy use in exactly this group without losing recurrence-free survival.
- Caveats: Fluorouracil and folinic acid alone; the trial says nothing about whether adding oxaliplatin changes the stage II calculus.; Enrolment ran from 1994 to 2003, before mismatch repair status was routinely known, and mismatch repair-deficient stage II tumours are now known not to benefit.; The 3.6 percent figure is a modelled absolute benefit conditional on an assumed baseline mortality.

## Sources

- Lancet 2007: https://doi.org/10.1016/S0140-6736(07)61866-2
- PubMed: https://pubmed.ncbi.nlm.nih.gov/18083404/

## Connected records

- key papers: [Circulating tumor DNA analysis guiding adjuvant therapy in stage II colon cancer (DYNAMIC)](https://onco.cc/key-papers/paper-tie-dynamic-ctdna-guided-adjuvant-stage-ii-colon-nejm-2022/), [Levamisole and fluorouracil for adjuvant therapy of resected colon carcinoma](https://onco.cc/key-papers/paper-moertel-levamisole-fluorouracil-adjuvant-colon-nejm-1990/), [Oxaliplatin, fluorouracil, and leucovorin as adjuvant treatment for colon cancer (MOSAIC)](https://onco.cc/key-papers/paper-mosaic-oxaliplatin-adjuvant-colon-nejm-2004/)
- cancers: [Colon cancer (adenocarcinoma of the colon)](https://onco.cc/cancers/colon-cancer/), [Colorectal cancer](https://onco.cc/cancers/colorectal/)
- fronts: [Chemotherapy](https://onco.cc/fronts/chemotherapy/)
- technologies: [Cytotoxic chemotherapy](https://onco.cc/technologies/cytotoxic-chemotherapy/)
- drugs: [Fluorouracil (5-FU)](https://onco.cc/drugs/fluorouracil/), [Leucovorin (folinic acid)](https://onco.cc/drugs/leucovorin/)
- institutions: [Oxford Cancer (Oxford University Hospitals and University of Oxford)](https://onco.cc/institutions/oxford-cancer/)
- terms: [Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR)](https://onco.cc/terms/msi/), [Neoadjuvant / adjuvant / perioperative](https://onco.cc/terms/neoadjuvant-adjuvant/)
- people: [Richard Gray](https://onco.cc/people/richard-gray/)
- bottlenecks: [Toxicity and quality of life are undervalued](https://onco.cc/bottlenecks/b-toxicity-qol/), [Trial design, endpoints and cost](https://onco.cc/bottlenecks/b-trial-design/)
- journals: [The Lancet](https://onco.cc/journals/lancet/)
- roadmaps: [Colorectal cancer roadmap: from the adenoma-carcinoma sequence and the first screening trials to total mesorectal excision, oxaliplatin, RAS testing, immunotherapy for mismatch repair-deficient disease, ctDNA-guided treatment and organ preservation](https://onco.cc/roadmaps/colorectal-roadmap/)

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