Breast Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_5_3372 - The Impact of Disparate Subtypes of Breast Cancer and Response to Postoperative Radiation Therapy in Neoadjuvant Setting

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

The Impact of Disparate Subtypes of Breast Cancer and Response to Postoperative Radiation Therapy in Neoadjuvant Setting
K. Jin1, J. Luo2, X. Chen2, Z. Yang2, J. Ma2, X. Guo2, and X. Yu2; 1Fudan University Shanghai Cancer center, Shanghai, China, 2Fudan University Shanghai Cancer Center, Shanghai, China

Purpose/Objective(s): To evaluate the effect of postoperative radiotherapy (RT) on disease free survival (DFS) and overall survival (OS) in different breast cancer subtypes in patients who underwent neoadjuvant chemotherapy (NAC) and mastectomy.

Materials/Methods: During August 2005 to December 2013, 594 breast cancer patients clinically staged II-III underwent NAC and surgery, 494 of which were administrated with postoperative RT. All patients were treated with anthracycline- and taxane-based NAC. Adjuvant RT dose to chest wall/whole breast and regional nodes was 50Gy in 25 fractions. Hormonal receptor (HR) and human epidermal growth factor receptor 2 (HER2) status were determined by immunohistochemistry before NAC. Multivariate analysis was performed by COX proportional hazard model.

Results: The median follow-up period was 60 months. In the whole cohort, multivariate analysis showed that postoperative RT could significantly improve DFS (hazard ratio [HR] 0.607, p=0.022), OS (HR 0.481, p=0.009) and locoregional recurrence free survival (LRRFS) (HR 0.309, p=0.004). Survival benefit of RT was more significant in the HR+ group in terms of DFS (HR 0.540, p=0.031) and LRRFS (HR 0.193, p=0.005) compared with the HR- group (p>0.1). RT could improve DFS (HR 0.433, p=0.008) and OS (HR 0.387, p=0.038) in HR+/HER2- group, while the effect of RT was not significant in HR+/HER2+ group (p>0.1). In the HER2+ group, patients treated with RT gained a borderline improvement in DFS (HR 0.474, p=0.073) and OS (HR 0.412, p=0.099). In the triple negative group, adjuvant RT showed no survival benefits (p>0.1).

Conclusion: The effect of postoperative RT was most prominent in HR+ patients, especially in HR+/HER2- group, but not significant in high risk subtypes. Therefore, other adjuvant treatments are warranted to improve the prognosis of high risk subtypes such as triple negative breast cancer.

Author Disclosure: K. Jin: None. X. Chen: None. J. Ma: None.

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