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Biologically Informed Decision-Making for PMRT in pT3N0M0 Luminal Breast Cancers (Protocol MF22-02): International
Atilla Soran1, Melis Bahadir Gultekin2, Bhanu Prasad Venkatesulu3
1Medical Center Magee-Womens Hospital, Surgical Oncology, University of Pittsburgh, Pittsburgh, PA.
Clinical Breast Cancer
|May 16, 2025
Summary
Postmastectomy radiation therapy (PMRT) may be safely omitted for select patients with luminal pT3N0M0 breast cancer (BC) and a low Magee Score (MS < 18). However, patients with a higher MS (≥ 18) benefit from PMRT to reduce loco-regional recurrence (LRR).
Area of Science:
- Oncology
- Radiation Oncology
- Breast Cancer Research
Background:
- Current guidelines lack definitive recommendations for postmastectomy radiation therapy (PMRT) in luminal pT3N0M0 breast cancer (BC).
- Emerging data supports de-escalation of radiation therapy (RT) in genomically defined, biologically favorable luminal BC.
- This study investigates the safety of omitting PMRT in this specific patient subgroup.
Purpose of the Study:
- To determine if PMRT can be safely omitted in patients with luminal pT3N0M0, hormone receptor (HR)-positive, HER2-negative breast cancer.
- To evaluate the impact of PMRT on overall survival (OS), loco-regional recurrence (LRR), and distant metastases (DM).
- To assess the role of the Magee Equations Score (MS) in predicting recurrence risk and guiding PMRT decisions.
Main Methods:
- Retrospective analysis of 202 women with pT3N0M0 HR-positive, HER2-negative BC who underwent mastectomy.
- Comparison of outcomes between patients who received PMRT (n=130) and those who did not (n=69).
- Analysis included factors like MS, menopausal status, axillary surgery, lymphovascular invasion (LVI), chemotherapy, and endocrine therapy.
Main Results:
- No significant difference in OS, local recurrence, or distant recurrence between PMRT and no PMRT groups.
- Patients receiving PMRT had higher rates of LVI, grade 3 tumors, and premenopausal status.
- For patients with MS < 18, LRR rates were similar regardless of PMRT (3% vs. 4%).
- For patients with MS ≥ 18, the no PMRT group had a significantly higher LRR rate (11% vs. 2%; P = .01), with PMRT associated with better LRR-free survival (HR 0.19).
Conclusions:
- Clinicians can use pathological risk factors and recurrence prediction models, like MS, to guide PMRT decisions for pT3N0M0, HR-positive, HER2-negative BC.
- Patients with MS < 18 have comparable recurrence rates whether they receive PMRT or not.
- Patients with MS ≥ 18 have higher LRR rates and should not omit PMRT.
Keywords:
Luminal typeMagee scorePostmastectomy radiotherapyRisk-adapted radiotherapypT3N0M0 breast cancer
