The effective duration of systemic therapy and the neutrophil-to-lymphocyte ratio predict the surgical advantage of primary tumor resection in patients with de novo stage IV breast cancer: a retrospective study.

Background: The primary tumor resection (PTR) of de novo stage IV breast cancer (DnIV BC) is controversial, and previous studies have suggested that the neutrophil-to-lymphocyte ratio (NLR) could be a poor-prognosis factor for BC. We investigated PTR's surgical advantage related to clinical outcomes, the surgery timing in responders to systemic therapy, and whether the NLR can predict the benefit of surgery for DnIV BC.

Patients and methods: We retrospectively analyzed the cases of the DnIV BC patients who received systemic therapies and/or underwent PTR at our institution between January 2004 and December 2022. Blood tests and NLR measurement were performed before and after each systematic therapy and/or surgery.

Results: Sixty patients had undergone PTR local surgery (Surgery group); 81 patients had not undergone surgical treatment (Non-surgery group). In both groups, systemic treatment was performed as chemotherapy (95%) and/or endocrine therapy (92.5%) (p < 0.0001). The groups' respective median progression-free survival (PFS) durations were 88 and 30.3 months (p = 0.004); their overall survival (OS) durations were 100.1 and 31.8 months (p = 0.0002). The Surgery-group responders to systemic therapy lasting > 8.1-months showed significantly longer OS (p = 0.044). The PFS and OS were significantly associated with the use of postoperative systemic therapy (p = 0.0012) and the NLR (p = 0.018). A low NLR (≤ 3) was associated with significantly better prognoses (PFS and OS; p < 0.0001).

Conclusions: A longer effective duration of systemic therapy (> 8.1 months) and a low pre-surgery NLR (≤ 3.0) could predict PTR's surgical advantage for DnIV BC. These variables may help guide decisions regarding the timing of surgery for DnIV BC.