Abstract: Objective: To explore the effects of chemotherapy on serum TGF-β1 expression in cancer patients with type 2 diabetes mellitus(T2DM).Methods: In accordance with a matched-pair study design, 40 patients were assigned to the experimental group(Group 1:malignant tumor with T2DM) and 40 others were assigned to the control group(Group 2;malignant tumor without T2DM).All patients underwent two cycles of chemotherapy.Two-milliliter samples of fasting venous blood were collected in the morning before and after the day of chemotherapy.Sera were separated and refrigerated at -40℃for further testing.Enzyme-linked immunosorbent assay was used to measure changes in the level of serum TGF-β1.Results: Differences in the expression of serum TGFβ-1 between Groups 1 and 2 before and after each cycle of chemotherapy were not statistically significant(P > 0.05).The expression of serum TGF-β1 decreased in Group 1 after the first cycle of chemotherapy: however, the serum level after the second cycle of chemotherapy increased compared with the content of serum TGF-β1 before the cycle started.The expression of serum TGF-β1 exhibited a continuous decreasing trend after both cycles of chemotherapy in Group 2, and the differences were statistically significant between them(P < 0.05).Conclusion: The expression level of serum TGF-β1 decreased after the first cycle of chemotherapy in both study groups, but it increased after the second cycle of chemotherapy in the experimental group.