The Dynamic Change in the Neutrophil–Lymphocyte Ratio and Systemic Inflammatory Response Index After Undergoing an Intensive Resistance-Based Exercise Program

<b>Background:</b> The change over time of certain inflammatory markers, such as the neutrophil-lymphocyte ratio (NLR) and systemic inflammatory response index (SIRI), is a prognostic factor in many cancers, including breast cancer. This study retrospectively evaluated how a 12-week intensive exercise program might have influenced both the NLR and SIRI in women with breast cancer. <b>Methods:</b> Two institutional review board-approved prospective clinical trials, EXERT-BC (NCT05747209, 2 November 2022) and EXERT-BCN (NCT05978960, 31 July 2023), were retrospectively assessed. Complete blood count (CBC) values performed before and after participation in a 12-week intensive resistance program were analyzed post hoc. Blood tests were ordered as part of routine clinical care and not pre-specified by either study protocol. Participants who had blood work more than four months from study intake or completion were excluded. Additionally, those undergoing active systemic therapy or with underlying inflammatory conditions were also excluded. The NLR and SIRI values were analyzed via the Mann-Whitney test, with pair-wise assessment of pre- and post-intervention values via the Wilcoxon signed-rank test. <b>Results:</b> Out of 84 participants, 21 people met the inclusion criteria. Roughly 70% had either ductal carcinoma in situ (DCIS) or early-stage breast cancer. The average blood draw was taken within two months of study intake and outtake. After the 12-week structured exercise program, there was an associated reduction in both the NLR (2.26 [IQR, 1.70-4.22] to 1.99 [1.44-2.62]; ΔNLR = -0.27, W = 47.0, <i>p</i> = 0.016) and SIRI (1.23 [0.82-1.64] to 0.80 [0.59-1.45]; ΔSIRI = -0.43, W = 48.0, <i>p</i> = 0.018). Of those who saw their inflammatory markers improve, roughly two thirds showed a clinically relevant improvement. <b>Conclusions:</b> Completion of a 12-week intensive resistance exercise program was associated with a statistically improved NLR and SIRI. The small sample size and retrospective nature limit the broader application of these findings. The results, however, provide a genesis for prospective validation examining the potential benefit exercise might have on the NLR and SIRI in women with breast cancer.