8.1.3 Radiotherapy After Breast Conserving Surgery...
Radiotherapy after breast-conserving breast cancer can significantly reduce the local recurrence rate of ipsilateral breast tumors.Meta-analysis showed that radiotherapy can also reduce distant metastasis rate and improve overall survival rate.The 10-year failure rate（local or distant metastasis）of patients with radiotherapy and non-radiation is 19.3%and 35%，respectively（p＜0.00001），15 years.Breast cancer mortality was 21.4%and 25.2%，respectively（p=0.0000），and the 15-year total mortality was 34.6%and 37.6%，respectively（p=0.03）.
Breast-conserving surgery patients，including various types of invasive cancer，whether the axillary lymph node is negative or positive，should generally be treated with postoperative radiotherapy.For example，in the NSABP B-06 randomized study，the 20-year local recurrence rates of patients after and after breast-conserving surgery were 14.3%and 39.2%，respectively.Patients with negative axillary lymph nodes and positive patients can benefit from radiotherapy.Patients with axillary lymph node-negative，radiotherapy and non-radiotherapy the recurrence rates of them were 17%and 36.2%，respectively；the 20-year local recurrence rates of patients with axillary lymph node-negative，radiotherapy and non-radiation were 8.8%and 44.2%，respectively.
Based on the current effective systemic therapy，combined with clinical low-risk factors and molecular typing，a group of patients without radiotherapy can be screened.CALGB9343 study enrolled patients with age≥70，T1N0M0（2/3 is cNO），surgical margin negative and ER-positive breast-conserving surgery，randomized to tamoxifen or postoperative radiotherapy+tamoxifen，5-year local recurrence rate of tamoxifen was 4%，the postoperative radiotherapy+tamoxifen group was 1%（P＜0.000）［10］.The 10-year local recurrence rate was 10%in the tamoxifen group alone，and the postoperative radiotherapy+tamoxifen group was 2%（P＜0.0001）.There was no difference in overall survival and breast cancer-specific survival（up to 98%and 97%）［11］.
After breast-conserving surgery，the patient underwent routine breast irradiation，and the conventional breast tangential field irradiation dose was 45-50 Gy，5 weeks，1 time/day，1.8-2 Gy/time.After the whole breast irradiation，the tumor bed should be supplemented with radiation.Clinically，if the surgical margin is negative，the tumor bed dose is 10-16Gy；if the surgical margin is positive，the tumor bed dose is 15-20Gy，which is routinely divided.The range of the tumor bed replenishment irradiation is determined according to the metal mark placed around the intraoperative tumor bed，the seroma after breast surgery and the postoperative change range of the CT image；the patient who has not placed the metal mark during the operation can refer to the physical examination and surgical scar location.(https://www.daowen.com)
Whether it is necessary to prevent lymph nodes in the breast cancer after breast-conserving surgery，and which regional lymph nodes are irradiated，mainly refer to the risk of subclinical involvement of regional lymph nodes at the time of initial diagnosis，the risk of postoperative lymph node recurrence，the efficiency of radiotherapy，the toxicity of radiotherapy，and the rescue after recurrence.The success rate of treatment and the effectiveness of systemic treatment to control distant subclinical lesions.In general，patients with pathologically negative axillary lymph nodes（axillary dissection or sentinel lymph node biopsy）do not require regional lymph node prophylaxis；patients with axillary lymph node metastasis≥4 need to prevent regional lymph nodes；patients with 1～3 axillary lymph node metastases need Patients with high risk factors are selected to prevent lymph nodes in the irradiated area.
The 2016 NCCN guidelines recommend that total breast radiotherapy be routinely divided，with a total dose of 46-50 Gy/（2Gy·23～25F）or a large division of 40-42.56Gy/15～16F（preferably large）.The tumor bed of patients with high recurrence risk is 10-16Gy/4～8F.According to the results of its own clinical research，the Cancer Hospital of the Medical College has a total breast segmentation of 43.5 Gy/（2.9 Gy·15F）and a tumor bed supplement of 8.7 Gy/（2.9 Gy·3F）.Large-segment radiotherapy that increases the single-dose dose and reduces the number of radiotherapy can shorten the radiotherapy cycle，enable patients to complete radiotherapy as soon as possible，reduce the number of patients returning to the hospital or shorten the hospital stay，and save medical resources.It is currently believed that breast cancer has a lower αβ value.From a radiobiological perspective，breast cancer large-segment radiotherapy can not increase the patient's late radiotherapy complications on the basis of ensuring efficacy.
The majority of patients with ipsilateral breast recurrence after breast-conserving surgery（about 80%）are located around the surgical incision.The tumor recurrence rate in other quadrants is about 15%，which is similar to the incidence of contralateral breast cancer.It may not be recurrence.Secondprimary cancer.Based on this，the clinical study of partial breast irradiation after breast conserving surgery was carried out abroad，and the scope of radiotherapy only included the area of the breast tumor bed.Part of the breast irradiation target area is reduced，and the irradiation method of accelerating the large segmentation can be adopted.The radiotherapy is completed in one week without causing a serious acute or late radiotherapy reaction.Accelerated partial breast irradiation（PBI）can reduce the dose of the heart，lung，chest wall and contralateral breast，but also reduce the dose of the ipsilateral mammary gland outside the tumor bed，which may improve the cosmetic effect of the breast and also cause recurrence after breast conserving surgery.It is possible for patients to undergo breast-conserving surgery and radiotherapy again.The PBI study was enrolled in low-risk patients.According to the long-term follow-up results of some phase Ⅱ clinical studies，the 2014 ASTRO PBI Consensus proposed the following appropriate conditions：age≥60，no BRCA 1/2 gene mutation，primary tumor maximum diameter≤2 cm，at least 2mm negative margin，single lesion center，no vascular tumor thrombus，ER negative，pathological invasive ductal carcinoma or other good type，pathology is not invasive lobular carcinoma，EC negative，axillary lymph node negative，no new adjuvant therapy.For the above patients，PBI may achieve the same efficacy as total breast irradiation.