In the past 40 years, the local recurrence rate of breast-conserving surgery plus whole-breast radiotherapy for early-stage breast cancer has decreased from 10% to 2%. Radiotherapy after total mastectomy can reduce the 5-year local-regional recurrence rate to 1/3-1/4 of the original rate in patients with positive axillary lymph nodes. Indications for postoperative radiotherapy for breast cancer1 After breast-conserving surgery for early-stage breast cancer, the first radiotherapy after breast-conserving surgery for early-stage breast cancer should be started within 4-6 weeks after surgery, after the incision has healed. Three-dimensional conformal or intensity modulation techniques can be used. The dose of whole breast irradiation is 45-50 Gy, 1.8-2 Gy/time, 5 times/week. After whole-breast irradiation, a top-up dose of 10-16 Gy is usually required in the tumor bed area, 5-8 times. In the absence of lymphatic drainage area irradiation, a “large split” regimen of 2.66 Gy, 16 doses, for a total dose of 42.5 Gy, or other biologically equivalent splits, may also be considered. Postoperative radiotherapy is required after radical or modified radical mastectomy for breast cancer with one of the following high-risk prognostic factors: 1. Maximum primary tumor diameter ≥ 5 cm, or tumor invasion to the breast skin or chest wall. 2.Lymph node metastasis ≥ 4. 3. T1/T2 patients with 1 to 3 lymph node metastases, including at least one of the following factors, are at higher risk of recurrence and radiotherapy is more meaningful: age ≤ 40 years, metastasis ratio > 20% when the number of axillary lymph nodes is < 10, hormone receptor negative, HER-2/neu overexpression, etc. The chest wall and supraclavicular area are the most common sites of recurrence and are the main target areas for postoperative radiotherapy. 3 questions that have to be faced when considering radiotherapy for T3N0 patients in breast cancer clinical practice : Is radiotherapy appropriate for all breast-conserving patients? Which patients are suitable for large split radiotherapy? Which patients need regional lymph node irradiation? Let's discuss them together. Which post-breast-conserving patients do not need radiotherapy? As mentioned above, although radiotherapy can reduce breast cancer recurrence and mortality, the benefit of radiotherapy is actually small in many subgroup analyses. Therefore, it is important to determine the appropriate population for radiotherapy. The CALGB 9343 study, which included 636 patients with 12.6 years of follow-up, confirmed that patients aged 70 years and older, with stage I pathology, positive hormone receptors, and negative cut margins had a low absolute recurrence rate and slow resolution of adverse effects such as breast edema and pain after whole-breast radiotherapy, and could be considered for endocrine therapy alone rather than radiotherapy. In this study, the incidence of distal metastases was 5%, and these were likely all Luminal A types. Based on the results of the PRIME II study, patients 65 years of age and older, with a maximum mass diameter ≤ 3 cm, who are hormone receptor positive, and who can receive standard endocrine therapy may also be considered for remission of postoperative radiotherapy. Radiation therapy after breast-conserving surgery should be screened for patients who can safely avoid radiotherapy based on the integration of molecular typing and traditional prognostic factors. Several studies are currently recruiting patients with ER-positive/HER2-negative Luminal A breast cancer for this study. There may be other types of breast-conserving patients who do not require radiotherapy, but at this time, studies have only confirmed these patient types. Which patients are candidates for large-split radiotherapy? Compared to conventional radiotherapy, large-split radiotherapy has many benefits, such as shorter treatment time and easier and more cost-effective radiotherapy. However, large fractionated chemotherapy is also more demanding in terms of equipment and technique. The START study, which included 4,451 patients followed up for nearly 10 years, showed that large fraction radiotherapy was safer and more effective than conventional fractionated radiotherapy, with lower distal metastasis rates, less damage to normal tissue, and higher overall survival rates. Based on the results of the START study, large fraction radiotherapy has been greatly used. However, high-dose lymph node irradiation and its potential to affect the upper brachial plexus nerve should be strictly limited in clinical practice. It is unclear whether the results of this study are an isolated case or are generalizable; evaluation studies are underway in the United Kingdom and Denmark, and results are expected to be published in the next few years. If the results are different, this could be a death blow for large-split radiotherapy. Which patients need regional lymph node radiotherapy? The ACOSOG Z11 study showed no difference in survival between axillary lymph node dissection and sentinel lymph node dissection after whole breast radiotherapy in patients with ≤ 3 positive axillary anterior lymph nodes for stage I-II breast cancer. Both the MA20 study and the EORTC study demonstrated a significant improvement in 10-year disease-free survival with regional lymph node radiotherapy in patients at intermediate risk of recurrence. Based on the results of the MA20 study, the freshly released 2016 NCCN guideline V1 has increased the recommendation for regional lymph node radiotherapy adaptation IIB to a Class I recommendation for ≥4 positive axillary lymph nodes and a Class IIA recommendation for 1 to 3 lymph nodes, respectively. Despite this change in the guideline, in fact, for patients with ≥4 positive axillary lymph nodes, the proportion of patients with positive internal breast area on previous extended radical mastectomy is only about 30%-40%, which means that 60%-70% of patients may be over-radiated if radiotherapy to the internal breast area is recommended as Class I. Regional lymph node radiotherapy can reduce the rate of local regional recurrence, but also has adverse effects. In the MA20 study, there was an increased incidence of grade 2 to 3 upper lymphedema, radiation pneumonitis, and increased doses of radiotherapy can damage the lungs and heart, which may predispose to other tumors. The focus of attention for the indication of regional lymph node radiotherapy is to balance the benefits and adverse effects of regional lymph node radiotherapy by considering the results of Z-11 and MA20 together. Biopsy of anterior lymph nodes in the internal mammary region is recommended to determine the presence or absence of metastasis in the internal mammary lymph nodes as a guide for individualized radiotherapy to the internal mammary region, but not for all patients with ≥ 4 positive axillary lymph nodes. Postoperative radiotherapy reduces the risk of recurrence and metastasis Two meta-analyses conducted by the EBCTCG after 2005 confirmed that radiotherapy after total mastectomy or breast-conserving surgery reduces the risk of local recurrence and death. The MA20 study showed that total breast irradiation + regional lymph node irradiation did not improve overall survival in breast cancer patients with positive or high-risk lymph node negative breast-conserving surgery or adjuvant systemic therapy, but significantly reduced the risk of recurrence and distant metastases. From 2008 to 2011, Professor Jay Harris of the DanaFarber Cancer Center in Boston demonstrated that local recurrence of breast cancer was primarily related to tumor subtype, HER2 status, and age, but not significantly related to treatment, tumor size, or lymph node status. For example, the 5-year local recurrence rate for triple-negative breast cancer was 6%, compared to 1% for Luminal A breast cancer; younger patients had a higher risk of recurrence than older patients.