Local surgery plus radiotherapy for early invasive breast cancer is the standard mode of breast-conserving treatment. The main radiotherapy modalities used after breast-conserving surgery are conventional radiotherapy (CR), three-dimensional conformal radiotherapy (3D-CRT), and intensity-modulated radiotherapy (IMRT). IMRT is superior to CR and 3D-CRT in terms of improving the target area uniformity and conformality and reducing the high-dose irradiated volume of the affected lung, and intensity-modulated radiotherapy has become the best choice for post-breast-conserving radiotherapy. In order to ensure the implementation of the “Three Precisions” (precise positioning, precise planning and precise treatment), it is necessary to ensure the consistency of the patient’s body position throughout the positioning and positioning process from tumor localization to treatment plan design, simulation, confirmation and daily repetition of treatment, therefore, treatment position and body fixation is an extremely important part of treatment plan design and execution. Therefore, treatment positioning and postural fixation is an extremely important part of treatment planning and execution. In breast cancer postoperative intensity-modulated radiotherapy (IMRT), the quality control of the thermoplastic fixation technique is strictly standardized and implemented, and the stability is better, the accuracy is greatly improved, and the quality of radiotherapy can be effectively ensured. As for some breast cancer patients who are not suitable for or unwilling to perform breast-conserving surgery, they choose modified radical surgery. Modified radical surgery is mainly used for non-invasive cancer or stage I invasive cancer, and stage II patients without obvious clinical axillary lymph node enlargement can also choose to apply. Breast cancer modified radical surgery I: mainly preserves the pectoralis major muscle and removes the whole breast and axillary lymphatic tissues; breast cancer modified radical surgery II mainly preserves the pectoralis major muscle and removes the whole breast and pectoralis minor muscle and axillary lymphatic tissues. The recurrence rate of breast cancer is higher if no radiation therapy is performed after radical surgery. According to the principles of radiation therapy after radical or modified radical surgery for breast cancer, some patients who choose modified radical surgery need to perform chest wall irradiation after modified radical surgery mainly in the skin, interstitial lymph nodes (and/or) and chest wall lymphatic drainage area under the breast because the breast tissue, pectoralis major muscle (and/or) pectoralis minor muscle are already intact intraoperatively. Inferior abdominal artery perforator flap breast reconstruction is performed mainly for certain breast cancer patients with excess tissue in the lower abdomen by grafting fat and skin from the lower abdomen as a musculocutaneous flap (Transverse Rectus Abdominis Musculocutaneous flap (TRAM)) to the chest wall to reconstruct a breast. The residual skin of the breast chest wall is removed as much as possible during total mastectomy, and the TRAM flap is used for breast reconstruction to reduce the recurrence of the residual skin of the chest wall. The application of modified radical mastectomy + inferior abdominal artery perforator flap breast reconstruction not only ensures the effectiveness of surgical treatment (modified radical mastectomy), but also (inferior abdominal artery perforator flap breast reconstruction) meets the aesthetic and psychological needs of breast cancer patients, while removing as much skin as possible from the breast wall can also reduce the chance of recurrence of residual skin on the chest wall. The scope of chest wall irradiation after modified radical breast cancer surgery + inferior abdominal wall artery perforator flap breast reconstruction is limited to the interstitial lymph nodes and the lymphatic drainage area of the chest wall under the breast. At present, with conventional radiotherapy and 3D-CRT, all the reconstructed breast, tumor bed, interstitial lymph nodes and submammary lymphatic drainage area are irradiated, so that the skin, reconstructed breast and other tissues with very low chance of recurrence are unnecessarily irradiated, resulting in serious local radiological side effects, such as skin contracture, fibrosis and contracture of the reconstructed breast.