Does Breast Cancer Subtype Impact Margin Status in Patients Undergoing Partial Mastectomy?

Area of Science:

• Oncology
• Surgical Oncology
• Breast Cancer Research

Background:

• Molecular subtypes of invasive breast cancer are crucial for guiding systemic therapy decisions.
• The role of molecular subtype in tailoring surgical therapy, specifically for achieving clear surgical margins, remains unclear.
• This study investigates the impact of breast cancer molecular subtype on surgical margin status in patients undergoing breast-conserving therapy (BCT) for stages I-III invasive breast cancer.

Purpose of the Study:

• To determine if breast cancer molecular subtype influences surgical margin status in patients undergoing breast-conserving therapy.
• To evaluate the association between molecular subtype (luminal, HER2-enriched, triple-negative) and positive margin rates after partial mastectomy.
• To inform surgical decision-making by assessing the predictive value of molecular subtype for margin status.

Main Methods:

• Analysis of data from two randomized trials focusing on cavity shave margins (CSM) and margin status after partial mastectomy (PM).
• Inclusion criteria required invasive carcinoma in the PM specimen and known ER, PR, and HER2 receptor status.
• Patients were categorized into luminal, HER2-enriched, or triple-negative (TN) subtypes. Margin status was assessed after standard PM, before CSM randomization.

Main Results:

• Molecular subtype showed significant correlations with patient race, tumor palpability, and tumor grade.
• No significant correlation was found between molecular subtype and Hispanic ethnicity or lymphovascular invasion.
• The overall positive margin rate was 33.7% and did not significantly differ across molecular subtypes (luminal: 33.7%, TN: 36.4%, P=0.425).

Conclusions:

• Molecular subtype is not a predictor of surgical margin status in patients with invasive breast cancer.
• Current findings indicate that molecular subtype should not independently guide surgical decision-making in breast-conserving therapy.
• Further research may explore other factors that influence margin status in different molecular subtypes.