# Oncotype DX Recurrence Score Predicts Survival in Invasive Micropapillary Breast Carcinoma: A National Cancer Database Analysis

## TL;DR

The Oncotype DX test can predict survival outcomes in a rare and aggressive type of breast cancer called invasive micropapillary carcinoma.

## Contribution

This study is the first to validate the Oncotype DX recurrence score as a prognostic tool for invasive micropapillary breast carcinoma patients.

## Key findings

- High Oncotype DX scores (>25) were associated with worse five-year survival in invasive micropapillary carcinoma patients.
- Low and intermediate Oncotype DX scores (≤25) showed similar excellent survival outcomes.
- Omission of radiation therapy and higher comorbidity burden were linked to worse survival in these patients.

## Abstract

Invasive micropapillary carcinoma (IMPC) is a rare and aggressive form of breast cancer that often spreads to lymph nodes early on. The 21-gene Oncotype DX test estimates risk of recurrence and guides chemotherapy use in common hormone-receptor-positive breast cancers, but its value in IMPC is unknown. Using the U.S. National Cancer Database, we identified women with early-stage IMPC who received Oncotype DX testing and were not treated before surgery. Patients with high scores (>25) had worse five-year survival than those with low (≤11) or intermediate (12–25) scores, while low and intermediate groups had similarly excellent outcomes. The assay therefore helps identify IMPC patients at higher risk and may inform decisions about adjuvant therapy, including radiation.

(1) Background: Invasive micropapillary carcinoma (IMPC) is a rare, aggressive breast cancer subtype marked by high lymph node metastasis rates. While Oncotype DX recurrence score (RS) offers prognostic information for patients with hormone-receptor-positive (HR+) breast cancer, its utility in IMPC—a histology with distinct biologic behavior—remains unvalidated. This study evaluates whether Oncotype DX offers prognostic information with respect to overall survival (OS) in non-metastatic, early-stage patients with IMPC of the breast. (2) Methods: The National Cancer Database (2004–2020) was queried to select for 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. (3) Results: A total of 1325 women met the selection criteria. The cohort demonstrated significant survival disparities by RS (log-rank p = 0.017). Five-year OS rates were 97.5%, 97.5%, and 93.7% for low, intermediate, and high-risk patients, respectively. Adjusted multivariate analysis confirmed RS as an independent prognosticator: low (HR = 0.31, 95% CI: 0.15–0.75) and intermediate (HR = 0.32, 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 (0 comorbidities vs. ≥2: HR = 0.25, 95% CI: 0.10–0.61) were significantly associated with worse survival. (4) Conclusions: Oncotype DX is predictive for 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.