Abstract P3-11-18: Prognostic significance of lobular versus ductal histology in HER2-positive breast cancer
Bibliographic record
Abstract
Abstract Background: Lobular HER2-positive (HER2+) breast cancer is a rare entity. As such, oncologic outcomes as compared to HER2+ breast cancer with ductal histology are not well-defined. Methods: We identified all non-metastatic HER2+ breast cancers treated with surgery in the province of Alberta, Canada from 2010-2017. We excluded those who had no exposure to trastuzumab. We compared clinicopathologic characteristics by histologic type, categorized as lobular, mixed ductal/lobular or ductal. We used Kaplan Meier methods and the log-rank test to compare recurrence-free survival (RFS) by histologic type. Multivariable Cox proportional hazards analyses were performed to evaluate the association between histology and RFS, adjusting for age, grade, ER status, pT stage and pN stage. Results: Among 1515 HER2+ breast cancer patients, 74 (4.9%) had lobular or mixed ductal/lobular histology (34 pure lobular and 40 mixed) and 1441 (95.1%) had ductal histology. Patients with lobular/mixed histology were older (median age 58.2 vs. 52.9, p<0.001) and had higher proportions of grade 1-2 disease (52.8% vs. 22.1%, p<0.001), ER-positive disease (95.9% vs. 74.3%, p<0.001) and pT3 disease (21.6% vs. 7.1%, p<0.001). Among 398 (26.3%) patients treated with neoadjuvant chemotherapy, the rate of pathologic complete response was 10.0% for lobular/mixed histology vs. 43.9% for ductal (p=0.04). At median follow-up of 4 years, there were 187 recurrences, 92 deaths with recurrence and 20 deaths without recurrence. 5-year RFS was 94.4% (95%CI: 66.6-99.2%) for lobular histology, 86.1% (95%CI: 66.7-94.6%) for mixed ductal/lobular histology and 87.0% (95%CI: 84.4-89.1%) for ductal histology (p=0.75) (Figure). In both unadjusted and adjusted analyses, neither lobular (adjusted HR 1.05, p=0.93) nor mixed histology (adjusted HR 0.71, p=0.46) were associated with worse RFS as compared to ductal histology. pT2-4 (vs. pT1) disease and pN2-3 (vs. pN0) disease were associated with worse RFS (all p<0.01). Results were unchanged in subgroup analysis restricted to ER-positive disease. Conclusion: While lobular cancers are known to be less sensitive to cytotoxic chemotherapy, our data supports that for HER2+ breast cancer treated with HER2-directed antibody therapy, lobular or mixed ductal/lobular histology is not a poor prognostic factor. Citation Format: Alison Laws, Yue Yang, MDSA MEng, Yuan Xu, Lisa Barbera, May Lynn Quan. Prognostic significance of lobular versus ductal histology in HER2-positive breast cancer [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 P3-11-18.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
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".