1.Make those who cannot be resected or critical resection to be able to be resected
2.For those who cannot be converted from anus-preserving surgery to anus-preserving surgery
3.Reducing distant metastasis caused by operation during surgery
Advantages of preoperative radiotherapy
1.Accurate positioning
2.Rich blood flow and high sensitivity of radiotherapy
3.Convenient for clinical evaluation of the efficacy of radiotherapy
4.Convenient to guide whether to perform postoperative radiotherapy
There are two methods of preoperative radiotherapy for rectal cancer.
I. High-dose preoperative radiotherapy
1. Advantages and indications.
(1) Transformation of inoperable tumors into operable ones (B3/C3 stage)
(2) To shrink tumor and reduce adhesion invasion
2.Irradiation dose and field setting.
(1)Dose: 40-45Gy;1.8Gy/F;5F/W
(2)Fields: primary tumor, peri-intestinal and pelvic lymphatic area
3. Time from surgery to radiotherapy: 3-4 weeks is optimal because.
(1) the tumor volume is still reduced 3-4 weeks after surgery
(2) the response to radiotherapy is obviously reduced 3-4 weeks after surgery
2.Low-dose preoperative radiotherapy
1. Advantages and indications.
(1) Reduce the distant metastasis caused by surgical operation
(2) For patients who can be resected in the middle or early stage of surgery
(3) No obvious regional lymph node metastasis
(4) Can not delay the time of surgery
2. Irradiation dose and setting field.
10-20Gy/1-3 days, surgery as soon as possible after radiotherapy