Surgical Therapy for Women with Multiple Synchronous Ipsilateral Breast Cancer (MIBC): Current Evidence to Guide Clinical Practice

Based on retrospective, historic data, surgeons have long recommended mastectomy as the surgical approach for women with multiple ipsilateral synchronous (multifocal or multi-centric) breast cancer (MIBC). In the modern era, however, local recurrence rates have significantly decreased due to improved imaging techniques and earlier detection through breast cancer screening, more accurate delivery of radiation, and the advent of targeted systemic therapies. Given the significant non-surgical advancements in the field of breast cancer care, the role of maximally invasive surgery in improving breast cancer outcomes has diminished. This raises the question as to whether the routine recommendation for mastectomy in MIBC is rooted in current evidence or archaic data. This review summarizes data regarding surgical options for women with MIBC.

The incidence of MIBC is increasing as a result of improved imaging modalities and the use of breast MRI for breast cancer screening and staging. MIBC tends toward more aggressive biology and higher rates of nodal positivity but recent data contradict the notion that more aggressive surgery improves outcomes. Retrospective studies and meta-analyses performed in the current era of targeted therapy and more sensitive breast cancer detection have demonstrated equivalent rates of local regional recurrence (LRR) in women with MIBC undergoing breast-conserving therapy (BCT) when compared stage to stage with women with unifocal disease. Alliance Z11102, the first national, prospective trial of breast conservation in the MIBC population in the USA, demonstrated the feasibility of BCT in this patient population with acceptable rates of conversion to mastectomy in the MIBC cohort. Prospective data regarding LRR and cosmetic outcomes for women undergoing BCT from completed clinical trials continue to mature, and new randomized clinical trials investigating the biology and treatment of MIBC are under design.

The incidence of MIBC is increasing due to screening mammography, improved quality of imaging, and the utilization of breast MRI for breast cancer screening and staging. Local regional recurrence rates in women with unifocal disease have decreased due to earlier detection and improved regional and systemic therapy. As adjuvant therapy improves, the extent of surgery is less impactful on LRR and long-term survival. Current data demonstrate acceptable LRR in women undergoing BCT for MIBC for whom negative surgical margins are achieved and appropriate adjuvant therapy is administered. While additional prospective data regarding biology, LRR, cosmesis, and long-term survival in women with MIBC continue to be collected, current evidence supports the role of patient choice in deciding between breast conservation and mastectomy in this population.