Abstract P5-10-06: Retrospective, population-based cohort study on associations between tumor size, receptor status, & regional nodal positivity rates for early-stage breast cancer: implications for decision between upfront surgery vs neoadjuvant systemic therapy
Bibliographic record
Abstract
Abstract Purpose: For clinically node-negative T1-T2 breast cancers, the ASCO/Ontario Health guidelines discourage staging axillary ultrasound (AxUS). At the same time, neoadjuvant systemic therapy (NST) is recommended for HER2-positive(+) and triple negative (TN) breast cancers over 2 cm, with controversy whether clinical T1cN0 HER2+ and TN breast cancers should receive NST or upfront surgery. We evaluated the rates of regional nodal positivity across T1a, T1b, T1c and T2 tumor sizes for hormone receptor (HR)+HER2-, HR-HER2+, HR+HER2+, and TN breast cancers. Methods: We performed a population-based, retrospective cohort study using administrative health databases at ICES Ontario. Data from all patients diagnosed with invasive breast cancer between 2000 – 2019 in Ontario, Canada were extracted from the Ontario Cancer Registry. Demographic, tumor, and treatment data were collected from the linked databases. The following variables were analyzed: T stage, number of positive regional lymph nodes, and estrogen, progesterone, and HER2 receptor statuses. The proportion of patients with positive lymph nodes was calculated for each receptor subtype. Chi-square tests (significance of P <0.05) with post-hoc Marascuilo correction were conducted. Analyses were conducted using SAS® and Python software. Results: There were 52,888 invasive breast cancers, including 39,265 HR+HER2- (74%), 5,511 HR+HER2+ (10%), 2,523 HR-HER2+ (5%), and 5,589 HR-/HER2- (11%). Increasing tumor size was associated with increasing rates of regional nodal positivity across all receptor subtypes (P < .001 for all). Among TN tumors, T1a lesions had a nodal positivity rate of 19% (95% CI 0.12 – 0.24), T1b 19% (95% CI 0.15 – 0.23), T1c 28% (95% CI 0.26 – 0.30), and T2 42% (95% CI 0.40 – 0.43). Among HR-HER2+ tumors, T1a lesions had a nodal positivity rate of 18% (95% CI 0.13 – 0.24), T1b 30% (95% CI 0.24 – 0.37), T1c 42% (95% CI 0.37 – 0.46), and T2 54% (95% CI 0.51 – 0.57). Among HR+HER2+ tumors, T1a lesions had nodal positivity rate of 23% (95% CI 0.19 – 0.29), T1b 20% (95% CI 0.17 – 0.25), T1c 32% (95% CI 0.29 – 0.34), and T2 56% (95% CI 0.54 – 0.58). Among HR+HER2- tumors, T1a had a rate of 16% (95% CI 0.15 – 0.18), T1b 16% (95% CI 0.15 – 0.17); T1c 30% (95% CI 0.29 – 0.30), and T2 54% (95% CI 0.54 – 0.56). For T1a lesions, nodal positivity rates were similar across all receptor subtypes. For T1b and T2 lesions, pairwise comparisons were significantly different between all receptor subtypes, except between HR+HER2+ and TN, and HR+HER2- and HR-HER2+, respectively. For T1c, HR-HER2+ had the highest rates of nodal positivity, followed by HR+HER2+, HR+HER2-, and TN (P < .001). Conclusion: While current guidelines discourage AxUS for cT1-T2N0 breast cancers, at the population-level, pathologic regional nodal positivity rates are not insignificant for T1-T2 tumors, especially TN and HER2+ tumors. Taking these patients with pathologically positive lymph nodes to upfront surgery results in undertreatment. Furthermore, for clinical T1c tumors, regional nodal positivity rates reached 42%, 32%, and 28% for HR-HER2+, HR+HER2+, and TNBC, respectively. These data need to be shared with patients with cT1c tumors when deciding between a NST or upfront surgery approach. Finally, we advocate that staging AxUS should be considered for all HER2+ and TN T1-T2 tumors, irrespective of tumor size. Citation Format: Yerin R. Lee, Vasily Giannakeas, David W. Lim. Retrospective, population-based cohort study on associations between tumor size, receptor status, & regional nodal positivity rates for early-stage breast cancer: implications for decision between upfront surgery vs neoadjuvant systemic therapy [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P5-10-06.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".