The unifying concepts of the sick lobe hypothesis, field cancerisation and breast conservation treatment for multiple ipsilateral breast cancers: a narrative review

Background and Objective: In the past, it was conventionally thought that multiple ipsilateral breast cancer (MIBC) was a contraindication to breast conservation surgery, especially if multicentric foci in different quadrants of the breast were present. However, over time, there has been a growing body of evidence in the literature demonstrating no survival detriment or poorer local control with breast conservation for MIBC. There is, however, a paucity of information integrating anatomy, pathology with surgical treatment of MIBC. Understanding mammary anatomy, pathology of the sick lobe hypothesis and molecular impact of field cancerisation contributes significantly to the understanding of the role of surgical treatment of MIBC. The purpose of this narrative overview is to review the paradigm shifts over time in the use of breast conservation treatment (BCT) for MIBC, and how the concepts of the sick lobe hypothesis and field cancerisation interact with this therapeutic strategy. A secondary objective is to explore the feasibility of surgical de-escalation for BCT in the presence of MIBC. Methods: A PubMed Search was performed for articles relating to BCT, multifocal, multicentric and MIBC. A separate literature search was performed for sick lobe hypothesis and field cancerisation and their interaction for surgical treatment for breast cancer. The available data was then analysed and synergised into a coherent summary of how the molecular and histologic aspects of MIBC interact with surgical therapy. Key Content and Findings: There is a growing body of evidence supporting the use of BCT for MIBC. However, there is scant data connecting the basic science aspects of breast cancer in terms of pathology and genetics to adequacy of surgical extirpation of breast malignancies. This review bridges this gap by demonstrating how information on basic sciences available in contemporary literature can be extrapolated for use in artificial intelligence (AI) systems to assist in BCT for MIBC.Conclusions: This narrative review connects several aspects of the surgical treatment for MIBC: historical perspectives of therapy compared with contemporary philosophy based on clinical evidence, anatomy/ pathology (sick lobe hypothesis) and molecular findings (field cancerisation) as potential indicators of adequate surgical resection, and how current technology can be used to forge future AI applications in breast cancer surgery. These form the foundation for future research to safely de-escalate surgery for women with MIBC.