Principles of radiotherapy for cervical cancer: Stage IIB or higher cervical cancer is the preferred treatment modality, stage I-IIA: either surgery or radiotherapy can be chosen, both of which have comparable efficacy. External-beam radiation therapy (EBRT) CT/MRI-based radiotherapy plan is the standard treatment for EBRT. MRI is most effective in determining whether the tumor has infiltrated the surrounding soft and parametrial tissues. EBRT requires coverage of the entire lesion, including the parametrium and the uterosacral ligaments, presacral lymph nodes and other potentially metastatic lymph nodes, as well as ensuring that the radiation field covers a certain area of normal vaginal tissue (at least 3 cm outside the lesion). If no lymph node metastasis is detected by surgery or no enlarged lymph nodes are detected by imaging, the volume of the radiotherapy field needs to include the external iliac lymph nodes, internal iliac lymph nodes and the base of the foramen ovale. If there is a greater risk of lymph node metastasis (e.g., large tumor volume, suspicion or finding of abnormal lymph nodes in the lower part of the true pelvis), the radiation field also needs to cover the common iliac lymph node area. In case of metastasis to the common iliac or para-abdominal aorta lymph nodes, an extended field radiotherapy is required, which needs to include the para-abdominal aorta with the upper border reaching the level of the renal vessels (the radiotherapy field may need to be extended further cephalad to include the involved lymph nodes). The radiotherapy dose is approximately 45 Gy for the treatment of microscopic microscopic lymph node metastases (routinely 1.8-2.0 Gy per day for fractionated radiotherapy), with additional highly conformal radiotherapy at a dose of 10-15 Gy if large confined lesions are present. most patients with cervical cancer receiving EBRT receive concurrent platinum-containing regimens of chemotherapy during radiotherapy (cisplatin alone or platinum-based + 5-FU/ paclitaxel). For patients who have had their uterus removed and who require radiotherapy to the para-aortic lymph nodes, intensity-modulated radiotherapy and other highly conformal radiotherapy techniques can help to reduce the dose of radiotherapy to the bowel and other vital organs. These techniques are also effective in patients who require high-dose radiation therapy for localized lymph node enlargement. However, in patients with unresected cervix and central lesions, conformal techniques such as intensity-modulated radiotherapy should not be preferred, and brachytherapy should remain the primary treatment modality. When using conformal radiotherapy techniques such as intensity-modulated radiotherapy, special attention should be paid to the design of the radiotherapy plan to ensure that the plan is reproducible. Accurate definition of target areas and normal tissues, consideration of the movement of internal organs and soft tissue deformation when patients receive radiotherapy, and regular physical quality control are important guarantees for the successful application of conformal techniques. Brachytherapy (internal radiation) Brachytherapy is an important complementary part of the initial treatment with radiotherapy. Brachytherapy can often be accomplished with an intracavitary applicator. The applicator consists of an intracavitary tube and a vaginal implant holder. If the patient requires external irradiation, brachytherapy can be administered in most cases in the later stages of radiotherapy, when the tumor has significantly reduced in size and brachytherapy instruments can easily reach the appropriate location. Some very early stage patients (e.g. stage IA2) can be cured by brachytherapy alone. If the tumor morphology is more specific and brachytherapy cannot be performed, interstitially inserted radiotherapy is preferable in this case. This type of treatment is best done by specialists from hospitals with relevant treatment experience. Stereotactic body radiation therapy (SBRT) is not an alternative to brachytherapy. Brachytherapy is guided by “3D imaging techniques” while protecting adjacent organs such as the bladder, rectum and intestines. Radical radiotherapy in primary cases The total radiotherapy dose for radical EBRT is mostly 45 Gy (40-50 Gy), and the volume of radiotherapy given for EBRT is determined by the status of the lymph nodes as determined by surgery or imaging. With combined brachytherapy, the primary cervical lesion will receive an increased dose of 30 to 40 Gy at site A (by dosing techniques such as LDR), at which point the total dose received at site A (recommended by guidelines) can reach 80 Gy (small cervical lesion volume) or ≥85 Gy (large cervical lesion volume). For significantly enlarged and unresected lymph nodes, additional doses of 10-15 Gy using conformal radiotherapy are required. when radiotherapy doses are higher, especially when EBRT is used, special attention needs to be paid to the tolerated dose of radiotherapy that can be accepted by normal tissues, and the dose received by normal organs located in the high dose area should be strictly controlled to avoid over-irradiation. Adjuvant radiotherapy after hysterectomy Adjuvant radiotherapy should be given after hysterectomy when high risk factors are identified on pathological examination. The radiotherapy field needs to include at least the following locations: 3 cm below the vaginal stump, parametrial tissue and the base of adjacent lymph nodes (e.g. external and internal iliac lymph nodes). If lymph node metastases are found, the upper boundary of the radiation field needs to be extended. If significantly enlarged lymph nodes are found, additional radiation doses of 10 to 15 Gy are required by conformal or intensity-modulated EBRT (volume reduction), and when radiation doses are high, especially when EBRT is performed, attention needs to be paid to the amount of radiation received by normal tissue in the high-dose area to avoid overdose.