Introduction to castration therapy for breast cancer

There are two commonly used preventive castration methods for breast cancer, namely surgical castration and radioactive castration. The two methods have the same castration effect. Surgical castration is quick to take effect and is mostly used for patients who are in good condition and need immediate castration (such as hypercalcemia, brain metastasis, etc.); radioactive castration is slow to take effect, generally taking 6-8 weeks, and is mostly used for weak patients who do not need immediate castration. To increase the efficacy, medical castration can also be used in combination.

Indications of castration therapy for breast cancer: Castration therapy is suitable for high-risk recurrence cases with extensive lymph node metastasis before menopause and estrogen receptor-positive patients. Its efficacy is mainly related to the patient's age. The best efficacy is achieved in premenopausal patients over 35 years old and within 1 year of menopause, which can reach more than 35%; the efficacy under 35 years old is only about 20%; and the efficacy is less than 6% for those who have been menopausal for more than 1 year. ER positivity, soft tissue metastasis, tumor-free survival for more than 2 years after surgery, and regular menstrual cycle are all favorable conditions for effective response. It is not suitable for estrogen receptor (ER)-negative patients, postmenopausal patients, and young cases.

1. Surgical castration. In 1896, Beatson first reported three cases of advanced breast cancer patients who achieved miraculous results after castration (oophorectomy). Since then, other reports have also clearly shown that oophorectomy can shrink the metastatic lesions of 1/3 to 2/5 patients with metastatic breast cancer, and the survival rate of effective patients is 2 to 3 times that of ineffective patients. Because therapeutic castration can indeed prolong the survival of patients, some researchers support preventive castration in the hope of preventing recurrence and then improving overall survival. Currently, bilateral oophorectomy has become one of the main treatments for premenopausal patients with advanced breast cancer, and can be used as a first-line method for ER-positive patients.

The efficacy of bilateral oophorectomy for advanced breast cancer is often not long-lasting. The reason is that after a period of time after oophorectomy, the estrogen in the blood begins to rise again, a small part of which is estradiol secreted by the adrenal glands, and most of it is androstenedione, an androgen precursor secreted by the adrenal glands, which is aromatized in the surrounding tissues. Therefore, for cases where oophorectomy is effective, adrenalectomy or other hormone treatments can be performed again.

Surgical removal of the ovaries is a quick and effective method with few side effects, and no auxiliary drugs are needed after the operation. Postoperative postmenopausal symptoms may occur, but they disappear quickly. Ovariectomy generally does not cause surgery-related deaths.

2. Radiation castration: a treatment method that achieves the purpose of castration by irradiating the ovaries to make them lose their function.

The design of castration irradiation for breast cancer is to find out the projection site of the ovaries on the body surface based on their anatomical position. If the patient's uterus is in a normal position, when the patient is in a supine position, a line is drawn between the midpoint of the line connecting the umbilicus and the anterior superior iliac spine and the midpoint of the pubic symphysis. The midpoint of this line is the body surface projection of the ovaries. If the patient's uterus is in an abnormal position, corresponding adjustments can be made based on the position of the uterus. When designing the irradiation field, the above-mentioned body surface landmarks are used as the basis, and after correction by B-ultrasound and CT examinations, the projection point of the bilateral ovaries is used as the midpoint of the ovaries. A 12×8cm2 or 10×5cm2 irradiation field is set, and cobalt 60 or high-energy X-rays are used. The absorbed dose of the ovaries is about 2000CGY/10 times/2 weeks, and the purpose of castration can be achieved.

It is generally believed that surgical castration and radiation castration have similar effects. However, surgical ovarian removal is more reliable and thorough, and the effect is faster; while the effect of radiation castration is delayed to several weeks or even months, and the elimination effect is not permanent. About 1/3 of patients still have menstruation after radiation castration. Therefore, for patients with advanced breast cancer, surgical castration is generally the first choice, and radiation castration is only used for patients who cannot undergo surgery due to other diseases or in cases where the tumor progresses slowly.