Effects of Reishimmune-S, a Fungal Immunomodulatory Peptide Supplement, on the Quality of Life and Circulating Natural Killer Cell Profiles of Patients With Early Breast Cancer Receiving Adjuvant Endocrine Therapy

To evaluate the effects of Reishimmune-S, a fungal immunomodulatory peptide, on the quality of life (QoL) and natural killer (NK) cell subpopulations in patients receiving adjuvant endocrine therapy (ET) for breast cancer (BC). Patients who received adjuvant ET for stage I-III hormone receptor-positive BC without active infection were enrolled in this prospective pilot study. Reishimmune-S was administered sublingually daily for 6 months. QoL scores, circulating immune cell levels, including lymphocyte/NK cell subpopulations, and plasma levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α were measured at baseline and every 4 weeks. Data were analyzed using linear mixed-effect regression models. Nineteen participants were included in the analyses. One patient with underlying asthma did not complete the study owing to the occurrence of skin rashes 15 days after the initiation of Reishimmune-S. No other adverse events were reported. Reishimmune-S supplementation significantly improved the cognitive function at 3 months and significantly decreased the fatigue and insomnia levels at 3 and 6 months, respectively. There was no significant change in the global health/QoL score between baseline and week 4 of treatment. The proportion of CD19 lymphocytes was significantly higher at 3 and 6 months, and that of NKG2A and NKp30 NK cells was significantly lower at 6 months than at baseline. In addition, fatigue positively correlated with the proportion of NKp30 NK cells (β ± standard error: 24.48 ± 8.75, = .007 in the mixed-effect model). Short-term supplementation with Reishimmune-S affected the circulating immune cell composition and exerted positive effects on cognitive function, fatigue, and insomnia in patients with BC undergoing adjuvant ET, providing a potential approach for the management of treatment-related adverse reactions in this patient population.