Long-term outcome of isolated locoregional (ILRR) breast cancer (BC) recurrence: a large retrospective Mono-institutional study

Background: Isolated locoregional relapse (ILRR) after curative treatment for early breast cancer (BC) is associated with poor prognosis. Treatment strategies are poorly standardized. We aimed at exploring prognostic factors and long-terms outcomes of ILRR. Patients and methods: Overall, 1070 patients diagnosed with stage I-III BC between 2000 and 2007 were identified from a large mono-institutional dataset, with long follow up. Among these, 66 patients (6%) presented an ILRR as first BC event and 33% subsequently presented a distant recurrence (DR) (22/66). Results: In the overall study cohort, patients with ILRR presented a significantly higher risk of DR compared to those without ILRR (p<.001). However, while being diagnosed with a DR was significantly associated with a worse overall survival (OS), ILRR was not.In the subgroup of patients with ILRR (N = 66), more advanced nodal status at initial diagnosis and HER2-positivity on the ILRR were significantly associated with worse distant relapse-free interval (DRFI) post-ILRR and worse OS post-ILRR. Moreover, switching from HR+ primary BC to HR- ILRR was associated with worse OS post-ILRR. In multivariate analyses, nodal involvement at primary diagnosis remained independently associated with both DRFI and OS post-ILRR, while HER2+ ILRR was independently associated with worse OS post-ILRR. Conclusion: Patients diagnosed with ILRR after curative treatment for primary BC are at higher risk of subsequent DR, highlighting the need for prompt diagnosis and treatment of ILRR. Moreover, biological recharacterization of ILRR provides potential key prognostic and predictive factors, such as HR loss, allowing personalization of treatment and follow-up after ILRR.