CPS+EG staging and local-regional recurrence after neoadjuvant chemotherapy
ForBreast cancer post-NACT without trastuzumab, cStage III or ypN+
TL;DR5-yr freedom from LRR by CPS+EG score spanned 71% to 99%, vs 86% to 97% by clinical or pathologic stage, in 1697 pts after NACT.
The PMRT read is in the CPS+EG ≤2 slice of the PMRT-indicated cohort (cStage III or ypN+): 5-yr LRR-free survival did not differ by local therapy (P=0.73), but only 72 pts had mastectomy alone. ER-positive or low-grade biology drives those low scores, so the proposed de-escalation gate is biology on top of residual nodal stage.
In cStage III or ypN+ disease after anthracycline/taxane NACT with ER-positive or low-grade biology (CPS+EG ≤2), this is hypothesis-level support for discussing PMRT omission; it does not extend to pts treated with neoadjuvant trastuzumab or to CPS+EG ≥3.
The omission signal sits in ypN+ or cStage III pts with CPS+EG ≤2 (N=358, P=0.73 across local therapies), the group PMRT policy treats by default. Field design, dose and target volumes are not reported, so nothing here speaks to nodal coverage or de-escalated volumes, only to the yes/no PMRT decision.
Mastectomy alone carried the highest crude LRR (8.1% vs 5.5% BCT) and significantly higher LRR risk on MVA vs BCT. After NACT, choosing mastectomy does not reduce local-regional risk on its own; BCT outcomes held across the cohort.
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Retrospective analysis of two MD Anderson cohorts used to build (932 pts, 1997 to 2003) and validate (804 pts, 2004 to 2005) CPS+EG; 39 excluded, N=1697. Median f/u 51 mo.
All pts received neoadjuvant anthracycline and/or taxane chemotherapy; median age 50. Neoadjuvant trastuzumab and preoperative RT excluded; 20 pts missing ER or grade also excluded.
Local therapy: BCT 656 (39%), mastectomy alone 297 (17%), mastectomy + PMRT 744 (44%). Institutional PMRT indications were clinical stage III, ypN+, or select cT1/T2N1 with high-risk features. Dose, fractionation and fields not reported in source.
LRR = invasive cancer in ipsilateral breast, chest wall or regional nodes, counted regardless of distant timing. Objectives: CPS+EG vs stage for LRR stratification, and whether a score threshold could identify pts safely omitting PMRT.
5-yr freedom from LRR 71% to 99% by CPS+EG vs 86% to 97% by clinical or pathologic stage. In the PMRT-indicated cohort with CPS+EG ≤2, local therapy type made no difference (P=0.73).
| Local therapy | N | LRR events | Crude LRR |
|---|---|---|---|
| Breast conserving therapy | 656 | 36 | 5.5% |
| Mastectomy alone | 297 | 24 | 8.1% |
| Mastectomy + PMRT | 744 | 50 | 6.7% |
| CPS+EG score | 5-yr LRR-free (%) | 95% CI (%) |
|---|---|---|
| 0 | 97.8 | 91.3–99.5 |
| 1 | 98.6 | 95.8–99.5 |
| 2 | 95.3 | 92.4–97.1 |
| 3 | 93.5 | 90.2–95.7 |
| 4 | 85.4 | 79.8–89.6 |
| 5 | 79.0 | 67.5–86.8 |
| 6 | 70.8 | 49.8–84.3 |
| Subgroup | BCT N | Mastectomy alone N | Mastectomy + PMRT N | P |
|---|---|---|---|---|
| CPS+EG 0-2 (N=358) | 114 | 72 | 172 | 0.73 |
| CPS+EG 3-6 (N=745) | 202 | 51 | 492 | 0.0006 |
NSABP B-18/B-27 (cited) reported 10-yr LRR of 10.3% with BCT and 12.3% with mastectomy but gave no PMRT, so cannot address it. The MD Anderson Prognostic Index omitted ER and grade. NSABP B-51 later randomized regional nodal RT in cN+ → ypN0, a different population from the ypN+ pts here.
Prose direction for the CPS+EG ≥3 subgroup (mastectomy alone favored) contradicts the MVA; overall LRR is reported as both 6.5% and 6.1%. Median f/u of 51 mo is short for ER-positive disease, the biology driving the favorable scores.
The stratification claim is sound and adds biology to anatomic staging for LRR. The omission claim is a null comparison in a small, selected subgroup with no equivalence margin, so it frames a trial question rather than settling one.
Retrospective single-institution cohort; the PMRT-omission claim rests on a non-randomized subgroup with confounding by indication and only 72 mastectomy-alone pts.
- Is PMRT omission safe in ypN+ pts with CPS+EG ≤2 beyond 5 years?
- Does CPS+EG stratify LRR after modern anti-HER2 or immunotherapy NACT?
- Prospective validation of biology-based PMRT selection after NACT active Standard or Comprehensive Radiation Therapy in Treating Patients With Early-Stage Breast Cancer Previously Treated With Chemotherapy and Surgery Phase NAn=1636 · primary completion 2023-09 · randomized regional nodal XRT vs none in ypN0 after NAC
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The longer read
This paper takes on a question randomized data had not answered when it was written: whether a pt with clinical stage III or residual node-positive disease after neoadjuvant chemotherapy and mastectomy needs PMRT. The authors argue that anatomy alone overstates risk for a subset whose tumors are ER-positive or lower grade, and that adding those two biologic variables to clinical and pathologic stage widens the spread of 5-yr freedom from LRR to 71% to 99%, against 86% to 97% for either staging axis alone. That stratification claim is the paper's strongest contribution. It uses the whole 1697-pt cohort, it holds up on multivariate analysis, and it carries a scoring system the same group had already built and validated for disease-specific survival over to a local-regional endpoint.
The PMRT-omission claim is weaker, and the reason is structural rather than statistical. Local therapy was chosen by the pt, surgeon and radiation oncologist under an institutional policy that routed clinical stage III and ypN+ pts to PMRT. In the CPS+EG ≤2 slice of the PMRT-indicated cohort, the pts who did not get PMRT were pts someone had already judged to be lower risk, and there were only 72 of them. A null log-rank result (P=0.73) in a 358-pt group with few events shows no detectable difference; it does not show equivalence. No confidence interval on the between-arm difference and no non-inferiority margin are given, and confounding by indication runs in the direction that flatters omission.
The reporting also needs a careful read. For the CPS+EG ≥3 subgroup, the text states that LRR-free survival was higher with mastectomy alone, which conflicts with the multivariate model where mastectomy alone carried significantly higher LRR risk and PMRT was marginally protective. The figure and text agree on significance (0.0006 and <0.001) but the prose direction looks inverted. The crude overall LRR is given as 6.5% in Results and 6.1% in Discussion. Neither changes the central argument, but both are reasons to want the per-arm rates before quoting this subgroup in a tumor board.
Against the literature the authors cite, the pooled NSABP B-18/B-27 experience had higher LRR (10.3% with BCT, 12.3% with mastectomy) but did not deliver PMRT, so it cannot inform the omission question, and the MD Anderson Prognostic Index scored anatomic and pathologic features without ER or grade. NSABP B-51 later tested regional nodal RT prospectively, but in cN+ pts converted to ypN0; the residual ypN+ pts at the center of this paper sit outside that trial, so for them this retrospective signal remains close to the best available framing.
Transferability is the main constraint for a current reader. The cohort was treated from 1997 to 2005 with anthracycline and taxane regimens, and pts given neoadjuvant trastuzumab were excluded, so HER2-directed and immunotherapy-containing regimens, which change both pCR rates and the biology of residual disease, are not represented. RT technique is not described. The 51-month median follow-up matters most here: the low-score group is defined largely by ER-positivity, the biology in which local-regional events accrue late. The way this result would turn out wrong is late recurrence beyond 5 years in exactly the pts it proposes to spare.