Risk Factors Associated with Pathological Complete Response and Its Impact on Outcomes in HER2-Low Breast Cancer...

Due to the lack of clinical trials of neoadjuvant chemotherapy (NAC) for patients with human epidermal growth factor receptor 2 (HER2)-low breast cancer, the factors influencing the efficacy of NAC for HER2-low breast cancer and the relationship between the efficacy of NAC and prognosis remain unclear. This study aimed to explore the risk factors associated with pathologic complete response (pCR) and their prognostic implications in a population of HER2-low breast cancer patients. We retrospectively analyzed data of patients with HER2-low breast cancer who underwent NAC in the Affiliated Hospital of Jiujiang College between 28st of February 2018 and 28st of February 2022. Clinical treatment and follow-up data were obtained from the patients' medical electric records. A total of 510 patients were enrolled, of which 443 were included in the initial non-matched analysis. The median age was 49.5 years (standard deviation (SD) = 8.0). Of these, 143 patients (32.3%) achieved pCR (case group), and 300 (67.7%) did not achieved pCR (control group). cStage (III versus II, odds ratio (OR) = 0.498), HR status (positive vs. negative, OR = 0.513), Ki-67 (>14% vs. ≤14%, OR = 2.580), tumor Nottingham stage (III vs. I, OR = 3.197), and endocrine therapy (yes vs. no, OR = 0.513) were independent predictive factors of pCR (all P < 0.05). After propensity score matching analyses, the control group included 80 non-pCR patients and the case group 80 achieved pCR. The clinical characteristics of the two groups were well balanced (all P > 0.05). The median follow-up period for the non-pCR and pCR groups was 43.0 (95% CI 41.0-45.0) and 45.0 (95% CI 43.1-46.9) months, respectively. The disease-free survival (DFS) of the two groups was 70.0% and 87.5%, respectively, which was a significant difference (P < 0.05). However, the overall survival (OS) of the two groups was 85.0% and 88.8%, respectively, with no significant difference (P > 0.05). After the Cox proportional hazards regression analyses, we found that cStage (III versus II, hazards ratio (HR) = 4.720), HR status (positive vs. negative, HR = 0.303), endocrine therapy (yes vs. no, HR = 0.303), and pCR (yes vs. no, HR = 0.312) were independent influencing factors of DFS (all P < 0.05); additionally, cStage (III vs. II, HR = 5.654) and HR status (positive vs. negative, HR = 0.292) and endocrine therapy (yes vs. no, HR = 0.292) were independent influencing factors of OS (all P < 0.05). The results showed that cStage, HR status, Ki-67, Nottingham tumor stage, and endocrine therapy were significantly correlated with the achievement of a pCR. Additionally, pCR was associated with a reduced risk of recurrence, but survival benefits were limited.