Relapse-free survival and metastasis-free survival between patients with breast cancer receiving adjuvant or neoadjuvant therapy: A retrospective study in Iran.

BACKGROUND

Breast cancer is the most common malignancy among women in Iran and worldwide. Although both neoadjuvant and adjuvant chemotherapies are widely used, their impact on relapse-free survival (RFS) and metastasis-free survival (MFS) in real-world settings remains unclear. This study aimed to compare RFS and MFS between neoadjuvant and adjuvant chemotherapy in breast cancer patients.

METHODS

A retrospective cohort study was conducted on patients who had received adjuvant or neoadjuvant therapy at Seyed Al-Shohada Hospital during July 2016 and July 2020. The cut-off date was July 202. Kaplan-Meier analysis and Cox regression models were used to evaluate RFS and MFS. To address potential confounding by indication due to non-randomized treatment assignment, inverse probability of treatment weighting (IPTW) was applied using propensity scores based on age, tumor grade, and molecular subtype.

RESULTS

Neoadjuvant therapy was significantly associated with increased relapse risk compared to adjuvant therapy in both multivariate (HR = 3.06, P = 0.030) and IPTW-weighted models (HR = 6.10, P = 0.002). No significant difference in MFS was observed between treatment groups. TNBC was identified as the strongest predictor of metastasis (HR = 6.45, P = 0.001). Subtype-specific analyses revealed better outcomes with adjuvant therapy in Luminal A and improved MFS/RFS with neoadjuvant therapy in TNBC.

CONCLUSION

Adjuvant therapy was associated with better local disease control (RFS), while MFS was primarily influenced by tumor subtype. These findings highlighted the importance of subtype-tailored therapeutic strategies and supported the use of causal methods such as IPTW in observational oncology research.