Background: Breast cancer is very common, and the incidence is growing every year. Most breast cancers are treated with radiation after surgery. As a side effect of radiation therapy, inflammation, as well as the neutrophil-lymphocyte ratio (NLR), level increases. However, high NLR levels act as independent prognostic factors for increased mortality in all cancers. In this study, the authors investigated whether administration of vitamin C, which is effective in suppressing inflammation, may help to reduce high levels of NLR produced by radiation therapy. Methods: This study was performed retrospectively among 424 patients who were diagnosed with breast cancer and were treated with postoperative radiotherapy at Kosin University Gospel Hospital from January 2011 to December 2017. Among them, 354 patients received radiation therapy without vitamin C (the control group), and 70 experimental patients received vitamin C intravenously twice a week for at least 4 weeks during radiation therapy. The experimental group was divided into two groups according to the dose administrated: a low-dose vitamin C group (less than 1 g/kg, 52 patients) and a high-dose vitamin C group (more than 1 g/kg, 18 patients). The authors conducted three NLR measurements: before and after radiation therapy and at 3 months after radiation therapy; the authors then compared the change in NLR over time between the groups using repeated measures analysis of variance. Results: In the control group and the low-dose vitamin C-administered group, NLR was increased at the endpoint compared to before the radiotherapy, whereas NLR values in the high-dose vitamin C group were 8.4 ± 1.7, 5.9 ± 1.3, and 4.3 ± 1.5, showing a continuous decrease and a statistically significant difference (pinteraction = 0.033). These results were similarly observed in models adjusted by the patient's age and American Joint Committee on Cancer stage, with borderline significance (pinteraction = 0.065). Conclusions: Elevated NLR, a measure of systemic inflammation, has been associated with higher mortality cancer patients, including breast cancer patients. In this observational study, NLR was significantly decreased during radiation therapy in patients administered high-dose vitamin C.
Keywords: breast cancer; high-dose vitamin C; neutrophil–lymphocyte ratio; radiotherapy.