OLIGOMETASTATIC BREAST CANCER: DEFINITIONS, DIAGNOSTIC ADVANCES, AND TREATMENT STRATEGIES

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Background: Oligometastatic breast cancer (OMBC) is considered an transitional state between locally confined and widespread metastaticbreast cancer. It is characterized by a limited number of metastatic lesions (commonly ≤5 lesions across ≤2 organs) and a potentially favorable response to definitive local therapies such as surgery or stereotactic body radiation therapy (SBRT).

Objective: To review recent advances in imaging and molecular biology in OMBC, elucidate the potential for long-term disease control through multimodal treatment strategies, and discuss ongoing challenges in standardizing diagnosis and management.

Content: Although metastatic breast cancer has traditionally been regarded as incurable, accumulating evidence suggests that a selected subgroup of patients with OMBC may achieve prolonged disease-free survival following aggressive treatment. However, there remains significant heterogeneity in the definition of OMBC across studies, including variations in imaging criteria, number and location of metastatic lesions, timing of metastasis (de novo versus metachronous), and molecular characteristics. The ESTRO-EORTC classification system has proposed 17 criteria for comprehensive assessment and distinguishes among different OMBC states, including genuine, induced, and repeat oligometastatic disease.

Most currently available data on OMBC management derive from retrospective studies and small phase II trials, while evidence from randomized controlled trials remains limited. This lack of high-level evidence poses challenges in standardizing treatment strategies, particularly regarding the role of local therapies in the context of increasingly personalized systemic treatment.

Recent advances in tumor biology and diagnostic technologies have opened new perspectives. Molecular biomarkers such as PIK3CA mutations, YAP/TAZ expression, and circulating tumor DNA (ctDNA) dynamics show promise in risk stratification, patient selection, and early detection of recurrence. Meanwhile, modern imaging modalities, including whole-body PET/CT with specific tracers, enable more accurate identification of metastatic burden and support appropriate classification of OMBC.

Conclusion: OMBC represents a distinct subgroup of breast cancer with unique prognostic implications and potential for improved outcomes. Accurate characterization of tumor biology combined with individualized treatment strategies may optimize clinical outcomes. Large-scale randomized trials are warranted to validate the benefit of aggressive interventions and to establish standardized treatment guidelines for this patient population.