The Role of Postmastectomy Radiotherapy in Breast Cancer Patients with 1-3 Positive Lymph Nodes: A Multicenter Retrospective Study from China

Abstract

The role of postmastectomy radiotherapy (PMRT) in women with pT1-2N1 breast cancer remains controversial. This multicenter retrospective study aimed to analyze the impact of PMRT on disease-free survival (DFS) and other outcomes in these patients in China. We retrospectively evaluated patients with pT1-2N1 breast cancer treated with mastectomy and axillary dissection between 2000 and 2014 in eleven Chinese hospitals. Those received neoadjuvant therapy were excluded. Locoregional recurrence (LRR), distant metastasis (DM), DFS, and overall survival (OS) rates were calculated. Propensity score matching (PSM) analysis was used to balance the PMRT and no PMRT groups. Subgroup analyses according to clinical factors were also performed. A total of 4869 patients were included. The clinical characteristics are listed in the table. Among them, 1571 (32.3%) underwent PMRT. While 4634 (95.2%) patients received chemotherapy and 3312 (88.6%) patients with ER or PR positive disease received endocrine therapy, only 26.4% of patients (n = 257) with HER2 positive disease received anti-HER2 target therapy. Compared with the no PMRT group, patients in the PMRT group had significantly more adverse factor including younger age, larger tumor size, more positive lymph nodes, and more ER/PR negative tumors, yet more patients in the PMRT group received chemotherapy and anti-HER2 therapy. After a median follow-up of 65.9 months, the 5-year DFS, OS, LRR, and DM rates of the whole cohort were 84.3%, 93.3%, 6.4%, and 11.3% respectively. Age, tumor location, primary tumor size, ratio of positive axillary lymph nodes, ER and PR status were independent risk factors associated with DFS in the whole group. PMRT significantly reduced LRR (hazard ratio (HR): 0.28; p<0.001), increased DFS (HR: 0.72; p = 0.026) and OS (HR 0.61, p = 0.002) in both univariable and multivariable analyses. In the PSM analysis including 2538 patients, PMRT significantly reduced LRR (HR 0.31, p<0.001) and increased DFS (HR 0.75, p = 0.003) and OS (HR 0.68, p = 0.011), but had no influence on DM. Subgroup analysis confirmed the benefit of PMRT, except in T1 tumors. PMRT may improve locoregional control and survival in women with pT1-2N1 breast cancer in China and should thus be omitted with caution.Abstract 2074; TableCharacteristicsAll (n = 4869) (%)PMRT (n = 3298) (%)no PMRT (n = 1571) (%)PAge year ≤40864 (17.1%)498 (15.1)366 (23.3)<0.001Tumor in inner or central location1255 (25.8)876 (26.6)379 (24.1)0.48Grade<0.001 I121 (2.5)100 (3.0)21 (1.3) II2734 (56.2)1859 (56.4)875 (55.7) III1075 (22.1)738 (22.4)337 (21.5)T stage<0.001 T12180 (44.8)1545 (46.8)635 (40.4) T22689 (55.2)1753 (53.2)936 (59.6)No of positive lymph nodes<0.001 12180 (44.8)1545 (46.8)635 (40.4) 21491 (30.6)950 (28.8)541 (34.4) 3924 (19.0)445 (13.5)479 (30.5) ER positive3450 (70.9)2391 (72.5)1059 (67.4)<0.001 PR positive3329 (68.4)2339 (70.9)990 (63.0) HER2 positive972 (20.0)663 (19.2)339 (21.6)0.02 Open table in a new tab