In a patient with only seven axillary nodes removed and all negative (0/7), should post‑mastectomy radiation therapy be administered, and what radiation regimen is recommended?

Post-Mastectomy Radiation Therapy for 0/7 Positive Lymph Nodes

PMRT is not indicated for patients with zero positive lymph nodes, regardless of the total number of nodes examined. 1

Primary Recommendation

• Do not administer PMRT when all examined axillary lymph nodes are negative (0/7 in this case), as the evidence shows no benefit and potential harm. 1
• The EBCTCG meta-analysis demonstrated that in node-negative patients after mastectomy with axillary dissection, PMRT actually increased 20-year all-cause mortality from 41.6% to 47.6% (relative risk 1.23, p=0.03), with no improvement in breast cancer mortality. 1

Critical Context: Adequacy of Axillary Sampling

While your patient has zero positive nodes, the adequacy of the axillary dissection matters for staging confidence:

• An adequate axillary dissection requires ≥10 lymph nodes removed to provide reliable staging. 2
• With only 7 nodes examined, the dissection is technically inadequate, which could theoretically underestimate nodal burden. 2
• However, since zero nodes are positive, the concern about understaging is minimal—even if additional nodes had been sampled, finding occult disease would be unlikely and would not change the recommendation against PMRT. 1

Exceptions That Would Change This Recommendation

PMRT should only be considered in node-negative patients if any of these features are present:

• Tumor size >5 cm (T3): Chest wall irradiation with or without regional nodal irradiation is indicated. 3
• Positive or close surgical margins: Chest wall irradiation should be considered. 3
• T3 tumors with positive nodes (not applicable here since nodes are negative). 1

Why PMRT Is Harmful in Node-Negative Disease

• The EBCTCG analysis of 700 node-negative patients showed PMRT reduced 10-year local recurrence from 3.0% to 1.6%, but this did not translate into survival benefit. 1
• Instead, 20-year breast cancer mortality was numerically higher (28.8% vs 26.6%, RR 1.18), though not statistically significant. 1
• The toxicity risks of PMRT—including lymphedema, brachial plexopathy, radiation pneumonitis, rib fractures, cardiac toxicity, and second malignancies—outweigh any minimal local control benefit when nodes are negative. 1

Common Pitfalls to Avoid

• Do not conflate inadequate nodal sampling with an indication for PMRT when all examined nodes are negative; the absolute number of positive nodes (zero in this case) determines treatment, not the total number examined. 1
• Do not extrapolate guidelines for 1-3 positive nodes to node-negative patients, even with high-risk features like young age or lymphovascular invasion—these factors do not justify PMRT in the absence of nodal involvement. 1
• Do not administer "prophylactic" regional nodal irradiation in node-negative disease; there is no evidence this improves outcomes and it increases toxicity. 1