Exploring the feasibility of exercise training during (neo)adjuvant chemotherapy in women with early-stage breast cancer: a pilot study examining immune and metabolic outcomes.

PURPOSE: To examine the feasibility and exploratory immunological, metabolic, and patient-reported effects of a supervised exercise intervention during (neo)adjuvant chemotherapy in women with early-stage breast cancer. METHODS: This non-randomised pilot study examined a 12-week supervised combined aerobic and resistance exercise programme during (neo)adjuvant treatment. Participants self-selected into the exercise intervention, and as no eligible participants opted for the control group, a convenience control group was subsequently recruited for blood biomarker comparisons. Sessions were performed 2-3 times per week-with exercise individually tailored according to treatment-related side effects and by progressively adjusting intensity to maintain a target rating of perceived exertion (RPE) of 12-16 (Borg 6-20 scale). Eleven patients (49.1 ± 14.4 years) completed the intervention and six (57.5 ± 5.4 years) comprised the convenience control group. Outcomes included feasibility (retention, attendance and adherence rates), immune cells, cytokines, metabolic biomarkers, body composition (lean and fat mass), health-related quality of life, and fatigue. RESULTS: Retention was 11/13 participants (84.6%), while attendance and adherence were 83.6 ± 23.1% and 77.9 ± 24.9%, respectively. Significant differences in immune cell subsets were observed, particularly within the cluster of differentiation 8 (CD8) + T cell compartment. Compared with controls, exercisers showed a greater increase in CD8 + effector memory re-expressing CD45RA (EMRA) cells (p = 0.019, Hedges' g = 1.26) and a reduction in CD8 + naïve T cells (p = 0.029, Hedges' g = - 1.16). Exercise prevented the insulin rise observed in controls (p = 0.034). Compared to baseline, body weight and fat mass were maintained, with a signal toward increased lean mass (0.8 kg, p = 0.093). Finally, exercise improved global quality of life (+ 16.7 points, p = 0.031) and showed a signal toward reduced fatigue (FACIT-F TOI + 8.4 points, p = 0.063). CONCLUSIONS: The supervised exercise programme was feasible among participants who enrolled in the intervention. Exploratory analyses suggest exercise may promote cytotoxic immune cell differentiation and mitigate metabolic dysregulation while significantly improving global quality of life. Larger trials are needed to confirm these findings.