Peritoneal Metastases from Breast Cancer: A Scoping Review

Breast cancer is the leading cause of cancer deaths amongst American women aged 20 to 59. While the incidence of breast cancer has been increasing, its mortality rates have significantly declined from 1989 to 2016. As a result, the number of survivors considerably increased. This impacts the detection and management of recurrences. Peritoneal metastases from breast cancer is a rare and challenging clinical presentation. There is a lack of knowledge syntheses and specific recommendations for the management of breast cancer peritoneal metastases. This review aims to determine the pattern of spread, prognosis, diagnosis, and role of surgery in this subset of patients. Relevant studies were searched in PubMed and Web of Science between April and June 2019. Included studies were written in English and reported data on breast cancer peritoneal or gastrointestinal metastases. Articles published before 1990, case reports, editorials, and articles with no full text available were excluded. Data abstraction was performed for citation information, population, sample, methods, relevant results, mentioned limitations, and study design. The search identified 505 unique reports. A total of 21 articles were included in the synthesis. Sixteen articles were observational studies, four were experimental, and one article was a proof-of-concept study. Amongst all observational studies, the diagnostic methods and criteria for breast cancer carcinomatosis were particularly heterogeneous, including ascites cytology, biopsy, surgical exploration, and various computed tomography (CT) findings. The majority of pathology and imaging reports demonstrated that breast cancer peritoneal metastases are mainly associated with invasive lobular carcinoma (ILC) and the following intrinsic subtypes: HER2-enriched, luminal B and basal-like. Experimental studies demonstrated that peritoneal metastases can be studied using breast cancer xenograft models. Somatic loss of both p53 and E-cadherin was associated with ILC peritoneal spread. Studies on prognosis and treatment highlighted that peritoneal metastases were associated with a poorer prognosis than other metastatic sites. In terms of surgical management, there is a paucity of data on the outcomes of hyperthermic intraperitoneal chemotherapy (HIPEC) in these patients. However, included studies suggested a role for cytoreductive surgery in selected patients when there is no residual disease after the procedure. This review summarizes data on the development, diagnosis, prognosis, and treatment of breast cancer peritoneal and gastrointestinal metastases. Patients' survival is significantly reduced in comparison with other distant metastatic sites. A deeper understanding of the invasion mechanisms and the role of surgery will be important.