Abstract P3-09-28: Long-term follow-up on survival outcomes in patients developing ipsilateral breast tumor recurrences

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Abstract Background: As more patients are treated with breast conserving surgery, there are increasing cases of patients experiencing the development of ipsilateral breast tumor recurrences (IBTRs). In this study, we aimed to investigate factors affecting survival outcomes in patients with IBTR. We placed special interest in addressing the relative importance of IBTR tumor characteristics in predicting survival outcomes in comparison with the characteristics of the initial breast cancer. Methods: This is a retrospective study that reviewed data of the patients who were treated at Seoul National University Hospital between January 2000 and March 2022 for their IBTRs. The study included only cases of invasive breast cancer recurrence, excluding cases of ductal carcinoma in situ IBTR. To identify the factors influencing distant metastasis-free survival (DMFS), we performed multivariate Cox proportional hazards regression analysis. Results: A total of 235 patients with IBTR were identified. The median follow-up period is 141.7 months and 60 patients developed distant metastasis during the follow-up. Survival analysis associated with both initial and IBTR tumor characteristics revealed distinct patterns of prognostic impact showing the features of IBTR tumors showing more significant associations with DMFS compared to the features of the initial tumors. Compared to T1 stage, T2 stage IBTR showed a two-fold increase in the risk of developing distant metastasis (95% CI, 1.03-3.87), while T3 or T4 stage tumors had a 4.2-fold higher risk(95% CI, 2.16-8.13). Triple-negative breast cancer (TNBC) IBTR demonstrated a 2.2-fold higher risk compared to HR+/HER2- subtypes (95% CI, 1.16-4.29). The presence of lymphovascular invasion in IBTR was associated with a 2.6-fold increase in risk(95% CI, 1.44-4.63). Notably, node-positive recurrence tumors did not show significant differences in DMFS compared to node-negative or non-dissected cases. In contrast, when examining the impact of initial tumor characteristics on DMFS, only lymphovascular invasion showed significant prognostic importance, with a 1.9-fold increased risk (95% CI, 1.12-3.34). The T stage, N stage, and subtype of the initial tumors did not significantly affect DMFS after the development of IBTR. Conclusion: In patients with IBTR, the characteristics of the recurrent tumor demonstrated more significant prognostic impact on DMFS compared to those of the initial tumors. These findings suggest that the biological features of the recurrent tumor, rather than those of the initial tumor, can be the primary basis for determining the risk of subsequent distant metastasis and guiding treatment decisions for patients with IBTR. Citation Format: Changhoon Lee, Eunhye Kang, Jong-Ho Cheun, Hyelim Kang, Min Jung Lee, Jinyoung Byeon, Ji-Jung Jung, Hong-Kyu Kim, Han-Byoel Lee, Wonshik Han, Hyeong-Gon Moon. Long-term follow-up on survival outcomes in patients developing ipsilateral breast tumor recurrences [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P3-09-28.

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