Effectiveness of Primary Tumour Surgery in Oligometastatic Breast Cancer for Improving Overall Survival: A Quasi-Experimental Study

Oligometastatic breast cancer (OMBC) is an entity is metastatic breast cancer with limited tumour burden. Usual nomenclature suggests total number of metastases to be less than 5 in up to 3 organs. It is considered an intermediate stage between localised and metastatic breast cancer. As compared to Multi metastatic stage 4 breast cancer oligometastatic breast cancer may have a favourable outcome (1,3) Currently the standard treatment for OMBC is systemic therapy (chemotherapy, hormone therapy or immunotherapy), with surgery or radiotherapy to primary tumour and metastatic sites as palliation only, as per ESMO and NCCN guidelines. (4,5) Retrospective observational studies suggested a possible survival benefit with primary tumour surgery (6,7). On the other hand, several Randomised controlled trials (Badwe et al., MF07-01, ECOG-ACRIN E2108, ABCSG-28) have shown inconsistent overall survival benefit with surgery in de novo metastatic breast cancer (8-10). The survival benefit has been observed where primary tumor surgery was performed in patients who respond well to systemic therapy in the form of complete or partial radiological response of metastasis, especially in patients with low metastatic burden, bone-only disease, or favorable biology may have differential outcomes after surgery (9,11).

Existing evidence is conflicting. So, case to case-based decision is being made for the oligometastatic breast cancer patients. There is a knowledge gap specific to oligometastatic disease among Pakistani patients as well. There are few Pakistani studies on this research question (12) The objective of this study is to determine whether surgical resection of the primary tumour in addition to standard systemic therapy improves overall survival compared with systemic therapy alone in patients with oligometastatic breast cancer.