Abstract: Objective  To analyze the effect of intensity modulated radiotherapy （IMRT） on long-term survival and immune function after breast conserving surgery for breast cancer. Methods Two hundred and fifty-four breast-conserving breast cancer patients were divided into observation group （n=147） and control group （n=147）. The patients were treated with whole breast irradiation 50 Gy／25 times after operation. In the supplementary radiotherapy of tumors， the control group was treated with electronic radiation， while the observation group was treated with X-ray IMRT. The prescription doses were 10-16 Gy／5-8 times. Dosimetry of target area， dosimetry of heart， dosimetry of affected lung， side effects， 5-year disease-free survival rate， 5-year survival rate and T cell subsets before and after radiotherapy were compared between the two groups. Results There was no significant difference in V95％ of target area of the tumor bed between the two groups （P＞0.05）. The V105％， V110％， cardiac irradiation dose and dose of affected side lung irradiation in observation group were （11.26±2.59）％， （3.15±0.84）％， （3.72±1.16） Gy and （7.51±2.06） Gy， which were lower than control group. The difference was significant （P＜0.05）. There was no significant difference in the incidence of acute skin reaction， late skin reaction， bone marrow suppression， radiation pneumonia and radiation esophagitis between the two groups （P＞0.05）. The 5-year disease-free survival rate of the observation group was 98.55％， which was higher than 94.16％ of the control group （P＜0.05）. The 5-year survival rate was 95.65％ in the observation group and 94.89％ in the control group， with no significant difference （P＞0.05）. After radiotherapy， the levels of CD+3， CD+4 and CD+4／CD+8 in the observation group were lower than those in the control group， and the level of CD+8 were higher than those in the control group （P＜0.05）. Conclusion X-ray IMRT after breast-conserving surgery for breast cancer can achieve better tumor-free survival， with little impact on immune function. It may be related to the uniform distribution of dose in the target area of the tumor bed and the reduction of radiation dose in the heart and lung of the affected side， which is worthy of clinical application.

Key words:

Breast cancer')">"> Breast cancer, Breast-conserving surgery, X-ray, Electronic line, Intensity-modulated radiotherapy（IMRT）, Immune function