Intervention to Hepatic and Pulmonary Metastasis in Breast Cancer Patients: Prospective, Observational, Multi-institutional Registration Study - IMET

Purpose Despite breast cancer being the most common cancer in women in the developed world, only a minority of patients (< 10%) has stage IV disease at diagnosis (1). In addition, 20-30% of patients with early breast cancer will experience distant metastatic relapse (2). Due to advances in available multimodality therapies and a better understanding of tumor biology, survival of stage IV patients is constantly improving (3-5).

Clinically, oligometastatic breast cancer is characterized by solitary/few detectable lesions, usually limited to single organs, in which local therapy with curative intent could impact survival. This population of 'potentially curable' stage IV disease is estimated to be 1-10% of newly diagnosed patients with metastatic breast cancer (5). A multimodal approach is endorsed for these selected patients (5,6). The identification of patients with truly oligometastatic disease is challenging. Most published series refer to an era before modern imaging (i.e. positron emission tomography-computed tomography), and thus many patients were probably understaged, potentially leading to underestimation of the global effect of an aggressive local management.

Patients with oligometastatic disease can be divided into 3 cohorts (7,8): 1) patients who present with oligometastases; 2) patients with residual oligometastases after systemic therapy; and 3) those with relapsed oligometastases after curative locoregional therapy. These different groups have possibly distinct prognoses, and may need differential approaches.

Several series have reported on lung and liver metastases resection in oligometastatic breast cancer and most data are from small series of patients collected over many years. The largest dataset comes from the International Registry of Lung Metastases and presents results of lung metastasectomy in 467 breast cancer patients (9). Complete resection was possible in 84% of patients and led to a median survival of 37 months (5-year OS = 38%, 10-year OS = 22%). Identified prognostic factors for lung resection include disease-free interval and number of metastases (disease-free interval >36 months and solitary metastases being the most favorable), ER status, size of metastases, completeness of resection, and use of anatomical resection (as opposite to wedge resection) (9-19). Obviously, the reported data refer to a subset of patients who were selected for favorable prognostic factors, and any comparison with surgically untreated patients is threatened by serious biases.

Pulmonary resection in metastatic breast cancer patients, apart from its potential therapeutic value, is also an important diagnostic tool, especially in patients with a suspected first recurrence, allowing for differential diagnosis with second primary lung cancers and benign lesions (19,20). The proportion of lesions proved not to be breast cancer metastases in various series ranges from 7% to 66% (9,14,18,21). As the morbidity and mortality of pulmonary resection has decreased substantially over the last decades, this potentially beneficial procedure can be discussed in a selected group of patients (9,19,21).