2942 - Prognostic Value of Oncotype DX in Invasive Micropapillary Carcinoma

03:00pm - 04:00pm PT

Hall F

Screen: 7

POSTER

Presenter(s)

Ali Haider, MD, BS - University of Texas Medical Branch, Galveston, TX

A. J. Haider^1,2, K. Chang³, W. Haque², E. Polychronopoulou⁴, J. S. Cummock⁵, S. S. Hatch^1,6, A. M. Farach², E. B. Butler², and B. S. Teh²; ¹Department of Radiation Oncology, The University of Texas Medical Branch, Galveston, TX, ²Department of Radiation Oncology, Houston Methodist Hospital, Houston, TX, ³John Sealy School of Medicine, The University of Texas Medical Branch, Galveston, TX, ⁴Department of Biostatistics & Data Science, University of Texas Medical Branch, Galveston, TX, ⁵Texas A&M University College of Medicine, Bryan, TX, ⁶Department of Radiation Oncology, MD Anderson Cancer Center, Houston, TX

Purpose/Objective(s): Invasive micropapillary carcinoma (IMPC) is a rare, aggressive breast cancer subtype marked by high lymph node metastasis rates. While Oncotype DX recurrence score (RS) predicts prognosis in hormone receptor-positive (HR+) breast cancer, its utility in IMPC—a histology with distinct biologic behavior—remains unvalidated. This study evaluates whether Oncotype DX stratifies overall survival (OS) in non-metastatic IMPC patients.

Materials/Methods: Using the National Cancer Database (2004–2020), we identified 1,325 women with ER+/HER2-, T1-T2N0-N1 IMPC who underwent Oncotype DX testing and received no neoadjuvant therapy. Patients were stratified by RS: low (=11), intermediate (12–25), and high (>25). Kaplan-Meier survival curves and log-rank tests compared 5-year OS between groups. Multivariable Cox proportional hazards models assessed RS as an independent predictor, adjusting for age, race, comorbidities, grade, radiation, and insurance status.

Results: The cohort demonstrated significant survival disparities by RS (log-rank p = 0.017). Five-year OS rates were 97.5% (low), 97.5% (intermediate), and 93.7% (high). High RS (>25) was associated with a 6.2% mortality rate, nearly triple that of low/intermediate groups (2.4/2.5%). Adjusted multivariate analysis confirmed RS as an independent prognosticator: low (HR = 0.34, 95% CI: 0.15–0.75) and intermediate (HR = 0.33, 95% CI: 0.15–0.75) scores correlated with reduced mortality versus high RS. Omission of radiation therapy (HR = 2.68, 95% CI: 1.05–6.86) and higher comorbidity burden (=2 comorbidities vs. 0: HR = 0.25, 95% CI: 0.10–0.61) were significantly associated with worse survival.

Conclusion: Oncotype DX predicts OS in IMPC, with high RS (>25) portending poorer outcomes. The survival detriment associated with RT omission aligns with prior studies demonstrating RT benefit in higher-risk cohorts. These findings validate RS as a prognostic tool in IMPC and underscore its potential to refine adjuvant therapy, particularly RT utilization. Future studies should explore RS-driven treatment personalization in IMPC, including comorbidity management and adjuvant radiation to improve outcomes in this distinct patient population.