The Absolute Effect / Evidence / Breast Cancer
AMAROS (EORTC 10981-22023)
Clinical question: In clinically node-negative T1–2 breast cancer with a positive sentinel node, can axillary radiotherapy replace completion axillary lymph-node dissection?
Registry: NCT00014612 · One underlying study; aliases and follow-up publications consolidated.
Design, population and eligibility
Phase III, multicentre, open-label randomized non-inferiority trial
4,806 patients underwent sentinel-node biopsy; 1,425 with a positive sentinel node were randomized: ALND 744 and axillary RT 681.
cT1–2, clinically node-negative invasive breast cancer with a positive sentinel lymph node. The evidence applies to sentinel-node-positive patients in the trial's early-stage setting, not bulky clinically node-positive disease.
Follow-up and endpoint maturity are stated with the reported efficacy results; further long-term updates are noted where applicable.
Treatment and comparator
Completion ALND versus axillary radiotherapy, 50 Gy in 25 fractions to axillary levels I–III and medial supraclavicular fossa. Adjuvant breast/chest-wall treatment and systemic therapy followed standard practice.
Primary and secondary endpoints
Primary endpoint: 5-year axillary recurrence, with a non-inferiority framework. Long-term outcomes include 10-year axillary recurrence, DFS, OS, morbidity and QoL.
Key efficacy results
At 10 years, cumulative axillary recurrence was 0.93% (95% CI 0.18–1.68; 7 events) after ALND and 1.82% (95% CI 0.74–2.94; 11 events) after axillary RT; HR 1.71 (95% CI 0.67–4.39). OS did not differ (HR 1.17; 95% CI 0.89–1.52) and DFS did not differ (HR 1.19; 95% CI 0.97–1.46).
At 5 years, clinical lymphedema was 24.5% after ALND versus 11.9% after axillary RT (P<0.001). QoL scales did not differ through 5 years.
Source-reported outcome visualization
Ten-year axillary recurrence and five-year clinical lymphedema.
Separate endpoint panels are reported as absolute rates. Rare axillary events mean the recurrence HR has a wide confidence interval.
Absolute effect
At 5 years, clinical lymphedema was 12.6 percentage points lower with axillary RT (11.9% vs 24.5%); approximate NNT 8 to prevent one additional case of clinical lymphedema at 5 years by choosing RT rather than ALND. The 10-year axillary recurrence difference was 0.89 percentage points higher with RT, but the confidence interval was wide and no NNT is assigned.
Trial-specific toxicity and treatment burden
Clinical lymphedema at 5 years: 24.5% ALND versus 11.9% axillary RT. Arm circumference increase >10% at 5 years: 13% versus 5%. Shoulder range of motion did not differ significantly. This is a morbidity trade-off: RT reduces surgical arm morbidity but carries regional radiation exposure and potential late effects. Do not conflate clinical lymphedema with the circumference-based measure.
Quality of life and patient-reported outcomes
Selected QoL scales (arm symptoms, pain and body image) did not show statistically significant clinically relevant differences through 5 years, despite less clinical lymphedema with RT.
Subgroups and applicability
The trial included breast-conserving surgery and mastectomy patients; it was not designed to establish management for patients with heavy nodal burden or gross residual disease. Contemporary practice must account for tumour burden and systemic therapy.
Current-practice context · reviewed 3 November 2026
Axillary RT is an established alternative to ALND for appropriately selected sentinel-node-positive cT1–2 patients when further axillary treatment is indicated. This study is distinct from trials testing omission of axillary surgery altogether.
Limitations and critical interpretation
The primary non-inferiority question was limited by very low recurrence rates; the 10-year HR CI is wide. The trial was not a direct comparison of RT versus no further axillary treatment. Modern systemic therapy and surgical de-escalation have changed the population treated.
Bottom line: AMAROS demonstrates excellent long-term axillary control with either strategy and materially less clinical lymphedema after axillary RT. It supports replacing ALND with RT in selected sentinel-node-positive patients, not universal axillary treatment omission.
Primary sources and follow-up publications
Outcome values are sourced from the linked reports. Unreported values are not imputed. NNT/NNH is only stated when an explicit fixed-time absolute difference supports a defensible calculation; no NNT is derived from median survival.