Treatment patterns and outcomes after metastatic recurrence following perioperative chemoimmunotherapy in triple-negative breast cancer (mTNBC).

e13131 Background: Data on the management and prognosis of metastatic recurrence after perioperative chemoimmunotherapy in TNBC are limited. Methods: We conducted a single-center cohort study to evaluate treatment patterns and clinical outcomes among patients with mTNBC who experienced distant recurrence after perioperative chemoimmunotherapy and were discussed at the multidisciplinary tumor board of the European Institute of Oncology (Milan) from Oct 2022 to Oct 2025. Endpoints were progression-free survival (PFS) and overall survival (OS), calculated from the start of first-line treatment. Results: A total of 62 patients were included. The median age at baseline was 48 years (IQR: 41-54) and 6% carried a germline BRCA pathogenic variant. 26% of patients did not complete the neoadjuvant phase of the KEYNOTE-522 regimen due to toxicity, comorbidity and/or disease progression; 92% had residual disease at surgery, 61% developed distant recurrence during perioperative treatment, and 94% within 1 year after its completion.First-line systemic therapy consisted primarly of antibody-drug conjugates (ADC, 57%), followed by chemotherapy (34%), chemo-immunotherapy (8%), and PARP inhibitors (1%).At a median follow-up of 10.5 months, 43 PFS events and 21 deaths were reported. The median PFS was 3.8 months (95%CI: 2.9-4.7), and was longer among patients treated with an ADC (4.6 vs. 3.1 months). The median OS was 18.9 months (95%CI: 4.4-23.3). Conclusions: Early distant recurrence following perioperative chemoimmunotherapy was associated with poor outcomes. The marked heterogeneity of postrecurrence treatment underscores the need for improved therapeutic strategies in this population.