Node-negative post-mastectomy LRR and prognostic factors
ForNode-negative breast, T1-3, mastectomy + ALND, no PMRT
TL;DR10y LRR 6.0% overall in N0 post-mastectomy pts without PMRT, rising to 40.6% with 3 risk factors (size >2 cm, margin <2 mm, premenopausal, LVI).
Chest wall was the failure site in 80.4% of total LRRs, which is the basis for the authors' chest wall-only field proposal in high-risk N0. The 3-factor stratum (10y LRR 40.6% ± 13.8%) sits near the node-positive LRR range where PMRT gained survival, but its wide error makes it a threshold argument, not an indication.
In node-negative pts after mastectomy with T2+ tumor, deep margin <2 mm and LVI (or premenopausal with any 2 of these), this supports discussing chest wall PMRT; it does not extend to N0 pts with 0 or 1 factors (10y LRR 1.2% and 10.0%).
Chest wall was the failure site in 80.4% of total LRRs, supporting chest wall-only fields over regional nodal coverage in high-risk N0. The 3-factor stratum (10y LRR 40.6% ± 13.8%) frames a risk threshold for discussing PMRT, not proof of benefit.
13 details 1 trial watching
Retrospective single-institution cohort (Massachusetts General Hospital), 1980-2000, identified via tumor registry and breast center databases. Median f/u 100 mo. LRR estimated by cumulative incidence (CIF); KM results reported as slightly higher, not substantially different.
877 node-negative invasive cases (870 pts) after mastectomy + axillary dissection, no PMRT; T4 excluded. Median age 64, median 15 nodes examined. Systemic therapy in 276 cases (148 hormones alone, 74 chemo alone, 54 both).
Total LRR (first event, with or without simultaneous distant mets) and isolated LRR (no distant mets for ≥4 mo). Only total LRR reported for prognostic factors.
10y total LRR 6.0%. Size >2 cm, deep margin <2 mm, premenopausal status and LVI independent on MVA with similar HRs (range 2.6 to 3.8). 3 factors: 10y LRR 40.6%; only 1 pt had all 4.
| Risk factors | 10y LRR |
|---|---|
| 0 | 1.2% ± 0.9% |
| 1 | 10.0% ± 2.9% |
| 2 | 17.9% ± 7.5% |
| 3 | 40.6% ± 13.8% |
| Factor | Adverse | Favorable | p |
|---|---|---|---|
| Deep margin | Close 22%, positive 21% | Negative 5.1% | <0.001 |
| LVI | Present 19.8% | Other 5.0% | 0.0001 |
| Tumor size | >2 cm 11% | ≤2 cm 3.1% | 0.001 |
| Menopausal status | Pre 11.1% | Post 5.1% | 0.01 |
| Grade | G3 10%, G2 5.3% | G1 0% | 0.03 |
| Site | Isolated LRR | Total LRR |
|---|---|---|
| Chest wall | 28 (87.5%) | 37 (80%) |
| Axilla | 2 (6%) | 3 (7%) |
| Supraclavicular | 1 (3%) | 5 (11%) |
| IMC | 1 (3%) | 1 (2%) |
No RT delivered. Chest wall was the site in 87.5% of isolated and 80.4% of total failures, so the authors propose chest wall-only PMRT without regional nodes for high-risk N0 to limit toxicity.
Converges with the IBCSG analysis of 1,275 N0 women on size, LVI and menopausal status, and adds margin status, which IBCSG could not assess. The M. D. Anderson series (141 N0 pts) did not report absolute LRR for its N0 subset.
Most cases (601/877) had no systemic therapy, so absolute risks likely overstate the modern setting. Receptor subtype not reported. LVI not recorded was pooled with absent, and the risk count assumes equal weights.
Authors suggest considering PMRT for postmenopausal pts with all 3 of T2+, close/positive margin and LVI, and premenopausal pts with any 2. Benefit of PMRT in these strata is inferred from risk level, never tested.
Retrospective single-institution 1980-2000 cohort with no PMRT arm; stepwise risk model unvalidated, high-risk strata small with wide SEs. Defines who might benefit, not benefit itself.
- Does chest wall-only PMRT reduce LRR in high-risk node-negative pts? recruiting Trial Evaluating Role of Post Mastectomy Radiotherapy in Women With Node Negative Early Breast Cancer Phase NAn=1022 · primary completion 2028-12 · PMRT in pT1-2N0 with adverse prognostic factors
- Do modern systemic therapy and receptor subtype lower these LRR estimates?
- Can biomarkers refine LRR risk beyond clinicopathologic factors?
📚 Sources · 📄 1 paper
The longer read
The headline 6.0% 10-year LRR confirms why node-negative mastectomy pts have generally not received PMRT. The paper's value is the gradient underneath that average. Four factors (tumor >2 cm, deep margin <2 mm, premenopausal status, LVI) each held up on multivariate analysis with hazard ratios in a narrow band, and that similarity is what licenses the authors' simple additive count. Once three coexist, 10-year LRR reaches 40.6%, a level the authors place beside the node-positive and T3 populations in which randomized PMRT data showed a survival gain. That is the core argument: nodal status is a proxy for LRR risk, and where the proxy misleads, the risk itself should drive the PMRT conversation.
How much weight the upper strata can carry is the first question. The 3-factor estimate carries a standard error of ±13.8% and the 2-factor estimate ±7.5%, which tells you these groups are small. Only one pt had all four factors. The model was built by stepwise selection from univariate hits in a single cohort with no validation set, which tends to overstate how cleanly the factors separate risk. Grade showed a univariate gradient (0%, 5.3%, 10%) but dropped out, more plausibly from overlap with size or LVI than from irrelevance. The LVI coding, which pooled unrecorded with absent, was a defensible call given pathology practice of the era; misclassification of that kind would tend to dilute the LVI effect rather than inflate it.
The era matters more than any single analytic choice. Cases span 1980 to 2000, 601 of 877 received no systemic therapy, and receptor and HER2 status are not reported in the source. The authors themselves concede that modern systemic therapy may lower these absolute risks, and that the higher LRR with combined chemo and hormones (12.6%) reflects selection rather than harm. The 40.6% figure is best read as an upper bound from an untreated-era population. The strongest support for the factors being real is convergence: the IBCSG analysis of 1,275 node-negative women found size, LVI and menopausal status predictive, and this cohort adds deep margin status, which IBCSG could not test because positive margins were excluded from its trials.
For the RT decision, the chest wall-only field proposal rests on the pattern of failure: the chest wall accounted for 80.4% of total LRR, with only 5 supraclavicular failures. That inference assumes failure sites in an unirradiated cohort predict where PMRT benefit lies, and it rests on 46 total events. The paper would be wrong in practice if modern systemic therapy and receptor-guided treatment compress the high-risk tail so that no N0 stratum approaches the LRR level of the node-positive trials. It defines a hypothesis about who might benefit from PMRT; it does not show that PMRT helps node-negative pts, since none were irradiated.