Impact of Neoadjuvant Chemotherapy Combined With Modified Radical Mastectomy on Immune Function, Oxidative Stress, and Prognosis in Patients With Different Molecular Subtypes of Breast Cancer

AIM: The objective of this study is to explore the impact of neoadjuvant chemotherapy (NACT) combined with modified radical mastectomy on immune function, oxidative stress and prognosis in patients with different molecular subtypes of breast cancer (BC). METHODS: A total of 150 patients diagnosed with BC who received NACT and modified radical mastectomy from January 2020 to January 2024 were collected for retrospective analysis. All patients were divided into four groups according to the molecular subtype: luminal A group (n = 39), luminal B group (n = 44), human epidermal growth factor receptor 2 (HER-2) overexpression group (n = 34), and triple-negative group (n = 33). Data on pathological complete remission (pCR), recurrence, recurrence-free survival (RFS) and overall survival (OS) were collected. The serum levels of malondialdehyde (MDA), superoxide dismutase (SOD), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor alpha (TNF-α) were detected using assay kits. RESULTS: The pCR rate of the entire sample cohort was 20.67% after NACT, with a recurrence rate during follow-up recorded at 22.67%. The pCR rate was significantly higher in the HER-2 overexpression group (13/34, 38.24%) than in the triple-negative (11/33, 33.33%), luminal A (1/39, 2.56%), and luminal B groups (6/44, 13.64%) (p < 0.001). Compared to the triple-negative (10/33, 30.30%), luminal A (5/39, 12.82%), and luminal B groups (6/44, 13.64%), the HER-2 overexpression group (13/34, 38.24%) had a significantly higher recurrence rate (p = 0.019). Both HER-2 overexpression and triple-negative groups also featured greater changes in IL-6, TNF-α, and SOD levels than the luminal A and luminal B groups (p < 0.05). Changes in MDA levels were the greatest in the HER-2 overexpression group among the tested group (p < 0.05). HER-2 overexpression was identified as the independent risk factor affecting RFS (hazard ratio [HR] = 3.883; 95% confidence interval [CI] = 1.371–11.004; p = 0.011). Clinical stage III (HR = 2.031; 95% CI = 1.023–4.030; p = 0.043), pCR (HR = 0.111; 95% CI = 0.015–0.809; p = 0.030) and recurrence (HR = 4.512; 95% CI = 2.412–8.441; p < 0.001) were the independent factors affecting OS in BC patients. The Kaplan–Meier curve analysis demonstrated significant differences in RFS among the four patient groups (p = 0.005), with no marked differences in OS (p = 0.303). The RFS of the HER-2 overexpression group was shorter than that of the other groups. CONCLUSIONS: In BC patients undergoing NACT combined with modified radical mastectomy, the HER-2 overexpression subtype was associated with a shorter RFS. However, no significant differences in OS were observed among the four molecular subtypes during the follow-up period. Inflammatory and oxidative stress markers showed improvements three months postoperatively across all subtypes, with more pronounced changes observed in the HER-2 overexpression and triple-negative subtypes.