1. Indications for radiation therapy after modified radical mastectomy for breast cancer: For postoperative systemic treatment including chemotherapy or/and endocrine therapy, one of the following high-risk factors is required for postoperative radiation therapy:
(1) The maximum diameter of the primary tumor is greater than or equal to 5 cm, or the tumor invades the breast skin or chest wall.
(2) Axillary lymph node metastasis greater than or equal to 4.
(3) Patients with 1-3 lymph node metastases in T1, T2 and T2, including one of the high-risk recurrence factors (age less than or equal to 40 years, hormone receptor negative, incomplete number of lymph node dissection or metastasis ratio greater than 20%, Her-2/neu overexpression, etc.) can be considered for post-operative radiation therapy.
2.Radiotherapy target area and dose.
(1) Superior/inferior clavicle field.
Upper border: the level of cricothyroid membrane.
Inferior border: it meets the upper border of the chest wall field, i.e. the level of the lower edge of the first rib.
Inner border: the medial border of the sternocleidomastoid muscle along the level of the midline of the body to the level of the sternotomy.
Outer border: the inner edge of the humeral head.
Irradiation dose: DT 50 Gy/5 weeks/25 times, a mixture of electron and X-ray irradiation can be applied to reduce the irradiation dose to the lung tip.
(2) Chest wall field.
Upper border: the lower border of the head of the clavicle, i.e. the lower border of the first rib.
Lower border: 1-2 cm below the skin fold of the contralateral breast.
Inner border: midline of the body.
External border: mid-axillary line or posterior axillary line.
Irradiation dose: Either X-ray or electron beam irradiation, whole chest wall DT 50 Gy/5 weeks/25 times.
The whole chest wall is routinely padded with compensator DT 20 Gy/2 weeks/10 times for electron beam irradiation to increase the surface dose to the chest wall. Ultrasound is routinely used to determine the thickness of the chest wall, and the thickness of the padding (tissue compensator) is adjusted according to the thickness of the chest wall, and the energy of the selected electron beam is determined to reduce the dose to the lung tissue and cardiac vessels to avoid radioactive lung injury as much as possible. When using X-ray tangential field irradiation, the chest wall compensation should be given to increase the skin dose.
(3) Axillary field irradiation. Axillary irradiation is required for those who do not have axillary lymph node dissection or incomplete axillary lymph node dissection.
(1) Combined supraclavicular and axillary fields.
Range of fields: supraclavicular and axillary areas, articulating with the chest wall field.
Dose: 6 MV-X ray, supraclavicular DT 50 Gy/5 weeks/25 times. The depth of the supraclavicular region was calculated as 3 cm subcutaneously. The axillary depth was calculated according to the actual measurement results, and the missing dose was used to make up the dose to DT 50 Gy in the posterior axillary field.
②Posterior axillary field.
Upper border: inferior border of the clavicle.
Inferior border: inferior border of the axilla.