J Breast Cancer.  2019 Jun;22(2):285-296. 10.4048/jbc.2019.22.e25.

The Benefit of Post-Mastectomy Radiotherapy in ypN0 Patients after Neoadjuvant Chemotherapy According to Molecular Subtypes

• Cho WK
• Park W
• Choi DH
• Kim YB
• Kim JH
• Kim SS
• Kim K
• Kim JH
• Ahn SJ
• Lee SY
• Lee J
• Kim SW
• Kwon J
• Ahn KJ

• KMID: 2450122
• DOI: http://doi.org/10.4048/jbc.2019.22.e25

Abstract

PURPOSE
The benefit of post-mastectomy radiation therapy (PMRT) in patients with breast cancer who achieve ypN0 following neoadjuvant chemotherapy (NAC) has not yet been established. This study aimed to identify the role of PMRT in patients who achieve ypN0 according to molecular subtype.
METHODS
We identified patients initially suspected with axillary disease who achieved ypN0 following NAC. From 13 institutions of the Korean Radiation Oncology Group between 2005 and 2011, a total of 189 patients were included in the analysis. Effects of PMRT on loco-regional control (LRC), disease-free survival (DFS), and overall survival (OS) were evaluated for different molecular subtypes.
RESULTS
In all patients, the prognostic effect of PMRT on LRC, DFS, or OS was not significant. Subgroups analysis showed that the effect of PMRT on LRC was different according to molecular subtype (p for interaction = 0.019). PMRT was associated with greater LRC in the luminal subtype (p = 0.046), but not in other subtypes.
CONCLUSION
In patients who achieve ypN0 following NAC and mastectomy, PMRT shows no additional survival benefits for any molecular subtype.

Keyword

Breast neoplasms; Mastectomy; Neoadjuvant treatment; Radiotherapy

MeSH Terms

Breast Neoplasms
Disease-Free Survival
Drug Therapy*
Humans
Mastectomy
Neoadjuvant Therapy
Phenobarbital
Radiation Oncology
Radiotherapy*
Phenobarbital

Figure

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  Figure 1 Patterns of failure in all patients.

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  Figure 2 Kaplan-Meier curves of LRR according to PMRT in subgroups by molecular subtype and residual breast disease. LRR according to PMRT in the (A) luminal subtype (n = 86), (B) HER2 subtype (n = 49), and (C) triple-negative subtype (n = 54). LRR = loco-regional recurrence; PMRT = post-mastectomy radiation therapy; HER2=human epidermal growth factor receptor 2.

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