Triple-negative oligometastatic breast cancer: A retrospective cohort.

e13000 Background: The optimal management of oligometastatic breast cancer (OMBC) remains undefined. Given its biological heterogeneity, subgroup-specific analyses are warranted. Data focusing on triple-negative (TN) OMBC are lacking. We aimed to describe the clinical characteristics, initial metastatic patterns, treatments, outcomes, and pattern of progression of a consecutive de novo TN OMBC and oligorecurrent TN metastatic breast cancer (MBC) cohort. Methods: We retrospectively identified all consecutive patients treated for de novo or recurrent MBC between 2012 and 2020 at a single institution. Among them, TN OMBC was defined as breast cancer with 1–5 metastatic lesions without hormone receptor or HER2 expression. Metastatic presentation, treatments including standard systemic therapy (SOC) and local ablative treatment (LAT), and patterns of progression at first relapse were analyzed. Survival outcomes were analyzed using the Kaplan–Meier method, log-rank tests and Cox proportional hazards models. Results: TN OMBC accounted for 49 cases, corresponding to 2.5% (49/1,980) of all metastatic breast cancers. 33% were de novo, while the remainder were metachronous, occurring before (29.2%) or after 24 months (37.5%). A single organ was involved in 81.6% of patients, and 1–3 metastases were observed in 87.8%. Distant lymph nodes were the most frequent metastatic site (38%), exceeding lung, liver, brain, and bone involvement. Overall, 28.6% of patients received local ablative treatment (LAT), either alone or combined with systemic therapy. No patients received immunotherapy during the study period. With a median follow-up of 75.9 months (95%CI 54.4; 82.0), median progression-free survival was 6.7 months (95%CI 4.8; 9.8) and median overall survival was 23.1 months (95%CI 17.2; 29.5). At 36 months, PFS was 10.4% (95% CI 3.8–20.9) and OS was 31.8% (95% CI 19.3–45.0). No prognostic factor was identified in univariable analyses including treatment, metastatic distribution, and metastatic chronology. After first-line treatment, 43 patients (87.7%) experienced disease progression. Local control was achieved in 47.9% of cases. Among patients with disease progression, 65.9% presented with oligoprogression. LAT targeting progressive lesions was administered in 23.3% of progressing patients. Conclusions: This study provides the first dedicated description of TN OMBC. TN OMBC is a rare clinical entity. The metastatic pattern showed a frequent involvement of distant lymph nodes. At three years, nearly one-third of patients are still alive. Following first-line systemic therapy, oligoprogression represented the predominant pattern of disease progression. Within the limitations of this retrospective study, these findings suggest that TN OMBC may represent a distinct clinical presentation compared with unselected TN metastatic breast cancer, and support further dedicated investigation.