Introduction:
The aim of the study was to investigate the changes in serum concentrations of nine vitamins in patients undergoing chemotherapy for lung cancer and explore their clinical values and influencing factors.

Material and methods:
Patients receiving chemotherapy for lung cancer in our centre from February 2018 to May 2020 were enrolled in this study. Serum concentrations of the nine vitamins including vitamins A, D, E, B9, B12, B1, C, B2, and B6 were measured in all subjects, and the changes in the concentrations of these vitamins were compared before and after 2 cycles of chemotherapy. In addition, the potential correlations of serum vitamin levels with age, gender, pathological type, and disease status were analysed.

Results:
In the 178 patients with lung cancer, there were different degrees of vitamin A, vitamin D, vitamin C, and in particular, vitamin B2 deficiencies. Before chemotherapy, the concentrations of vitamin A and vitamin C were significantly different between males and females and among patients in different clinical stages (both p < 0.05), the concentrations of vitamin C and vitamin B2 significantly differed among different pathological types of lung cancer (p < 0.05), and vitamin D level was significantly related to the disease status (p < 0.05). In addition, the proportion of vitamin B2 deficiency differed significantly among different pathological types (p < 0.05). There were significant differences in the concentrations of vitamins D, C, and B2 before and after chemotherapy (all p < 0.05). There was a correlation between the change of serum vitamin B1 concentration before and after chemotherapy and the change of body mass index (p < 0.05).

Conclusions:
During chemotherapy, lung cancer patients are more likely to develop vitamins A, D, C, and B2 deficiencies. Different vitamin deficiencies are related to gender, clinical stage, pathological type, and disease status. Vitamin determination and reasonable supplementation of nutrients in patients undergoing chemotherapy for lung cancer can help improve the nutritional status and increase chemotherapy tolerance.