This study aimed to investigate the clinical efficacy of combining docetaxel with radiotherapy in breast cancer patients who have undergone surgery. 110 breast cancer patients admitted to our hospital were selected between January 2023 and June 2023 and randomly allocated into two groups (n = 55/group) using a randomized numerical table method. After surgery, the control group received docetaxel, while the study group received docetaxel in conjunction with X-ray intensity-modulated radiation therapy. Their clinical effectiveness, tumor markers, DNA methyltransferase (DNMT1), oncogene cripto-1 (CP-1), and CUE structural domain protein 2 (CUEDC2) expression levels and adverse events were compared before and after treatment. After treatment, we found no significant differences in T lymphocyte subpopulation indices between the two groups (p > 0.05), while the study group had significantly lower levels of all tumor markers, including DNMT1, CP-1 and CUEDC2, compared to the control group (p < 0.05). The incidence of adverse events in the study group (9.09%) was slightly higher than in the control group (5.45%), but the difference was not statistically significant (p > 0.05). In summary, postoperative docetaxel combined with X-ray intensity-modulated radiotherapy may lower tumor marker levels, inhibit malignant tumor cell behavior, enhance overall clinical efficacy, and extend patient survival without significantly impacting immune function or increasing the risks of adverse effects.