The age distribution of breast cancer in white women is very different from that of Chinese women, with about 25% of patients in the former having an age of onset <50 years and 6% <40 years. In contrast, statistics from Shenyang, China, in 2005 showed that about 51% of patients had an age of onset <50 years and 11% <40 years. There are also many data that show that the proportion of young and middle-aged patients with breast cancer in China is significantly greater than that in Europe and the United States. Due to cultural, educational and occupational factors, there has been a worldwide trend in the last 20 years to increase the number of women over the age of 30 who are pregnant and giving birth. In the United States, the percentage of first-time mothers over 30 years of age has increased from 4% in the early 1990s to 21% today. Foreign data show that 50% of breast cancer patients under the age of 40 are concerned about future fertility at the time of diagnosis, worried about infertility caused by chemotherapy and other treatments, and a significant proportion of patients hope to regain fertility after breast cancer treatment. Therefore, the American Society of Clinical Oncology began to recommend in 2006 that for this group of patients, breast cancer specialists should introduce the relevant knowledge and concepts to patients in conjunction with their wishes, and recommend to doctors specializing in obstetrics and gynecology and reproduction to collaborate in designing or adopting measures and methods to protect fertility as much as possible, so that patients can satisfy their fertility wishes and improve and enhance their quality of life as much as possible after breast cancer treatment. 1. Is there any evidence that pregnancy after breast cancer treatment has an impact on the survival of recurrent metastasis of the disease? In the past, it was thought that pregnancy after breast cancer was detrimental to disease recovery. At that time, the view was that when pregnant, the tissues were exposed to high levels of ovarian estrogen and progesterone stimulation, so breast cancer patients were advised not to become pregnant. However, modern evidence-based medical data suggest that pregnancy after breast cancer does not increase the risk of recurrence and may even have a protective effect. In several case-control retrospective studies, overall survival was longer in the pregnant group than in the non-pregnant group when compared by the same age, stage of disease group. A meta-analysis that pooled 14 such studies found that 1244 patients who became pregnant after breast cancer had a 41% lower risk of death in the pregnant group compared with 18,145 patients who did not become pregnant. It is thought that one of the reasons for this is that there may have been a "bias" in the selection of patients for the study. This is because women who become pregnant after breast cancer are "relatively healthy mothers" and therefore have a good prognosis. Some experimental studies have found that in vitro, high concentrations of estrogen and progesterone in the pregnant state can induce the death of endocrine-responsive breast cancer cells. In addition, the fetal antigen hypothesis suggests that in pregnancy, the maternal immune system is activated and stimulated to fight breast cancer cells. The true impact of pregnancy on breast cancer needs to be illustrated by data from rigorously designed prospective studies. Despite more recent evidence that pregnancy after breast cancer does not increase the risk of recurrence, studies have found that not many women, only 3-15%, actually become pregnant and have children after breast cancer. The reasons for this may be: treatment-induced infertility; fear of recurrence; lack of counseling guidance; and the patient's own choice not to have children. Therefore, it is essential to provide reasonable medical counseling and psychosocial assistance to breast cancer patients who wish to have children. 2.Does adjuvant treatment for breast cancer impair the function of the ovaries? Ovarian function begins to decline at an accelerated rate around the age of 35. There are 300,000 follicles at puberty, but by the age of 35, it has decreased to only 25,000 follicles. Chemotherapy has a clear negative impact on ovarian function and fertility. The main manifestation is that chemotherapy can cause transient amenorrhea or permanent amenorrhea. The most toxic chemotherapeutic agent to the ovaries is cyclophosphamide, and amenorrhea is highly correlated with the age of the patient; in those under 30 years of age, there is almost no amenorrhea, and in those 30-35 years of age, the chance of amenorrhea is less than 10%. In patients older than 40 years old, amenorrhea occurs in 30-80% or even 90% of patients. Younger breast cancer patients tend to resume menstruation within 6-12 months after chemotherapy. This is because the developing follicles are destroyed by the chemotherapy drugs and it takes time for new follicles to grow from the basal follicular pool. The effect of tamoxifen on ovarian function is inconclusive. The toxicity of radiotherapy to the ovaries is minimal, and only very few rays reach the pelvis during radiotherapy. 3. Will adjuvant therapy affect the fetus? A major concern of patients is whether chemotherapy drugs for breast cancer have potential teratogenic effects? There have been few studies on the health status of babies born in pregnancy after breast cancer treatment. Overall, the health status of the next generation is no more risky than that of the general population. However, a study by the Breast Cancer Collaborative Group of 5,752 post-breast cancer pregnancies found a high rate of elective abortions, 20-44%, which may reflect concerns of patients and physicians about the safety of post-breast cancer pregnancies. I review the recent clinical study of 2 groups of pregnancies after adjuvant chemotherapy for ovarian cancer reported in China, in which more than 40 patients gave birth to healthy babies and only one case was induced due to abnormality found in the middle of pregnancy. 4. What are the feasible methods to protect the reproductive function? The most effective and feasible method is embryo cryopreservation. This involves delaying chemotherapy for 2-3 weeks. Usually, systemic chemotherapy can be started 2-3 weeks after breast cancer surgery. However, it usually takes 2-3 weeks to stimulate the ovaries with drugs and then to obtain the eggs. Therefore, patients should be referred to a fertility specialist before or immediately after breast cancer surgery to avoid delays in chemotherapy. This is actually done using "IVF" technology. Four million babies have been born worldwide using IVF. When the systemic treatment for breast cancer is over, the embryos are implanted in the uterus to complete the pregnancy. In our country, this is more appropriate for patients over 30 years old who have a spouse. For those without a partner, it is recommended abroad that sperm from a sperm bank can be borrowed for in vitro fertilization and then the embryos can be frozen. It is also possible to consider just freezing the eggs or ovarian tissue. However, these are still experimental techniques, with the former reporting over 500 successful births and the latter reporting 100 cases. There are also several large fertility centers in China that are conducting trial attempts in this area. 5. Can the damage to ovarian function caused by chemotherapy be reduced with analogues of GnRH? GnRH is gonadotropin-releasing hormone, which is a hormone secreted by the hypothalamus and acts on the pituitary gland. There are three analogues of this hormone in clinical use. When applied to breast cancer patients, it can lead to amenorrhea, and menstruation resumes after stopping the drug, so it is equivalent to "removing the ovaries" with the drug. Studies have long been concerned about whether the use of these drugs during chemotherapy can protect the ovaries. More recently, in the July 2011 issue of the Journal of the American Medical Association (JAMA), Italian scholars published a multicenter clinical study showing that the application of GnRH analogs resulted in a significant reduction in the proportion of amenorrhea caused by chemotherapy for breast cancer. Therefore the latest conclusion of this answer is tending to be positive. More and more breast cancer centers in China have also started to combine GnRH analogues with chemotherapy for young breast cancer patients to protect ovarian function. 6.How long should I wait to get pregnant after breast cancer? For patients with low risk of recurrence, the prognosis of those who become pregnant and give birth within 2 years does not seem to be affected. However, it is more recognized that it is safer to get pregnant after 2 years of breast cancer treatment because the high-risk period of recurrence has been passed. It is safer to get pregnant 6 months after the end of chemotherapy and 3-6 months after the endocrine therapy. 7.Can patients breastfeed after breast cancer? Breastfeeding is the preferred and recommended feeding method today. However, there is a lack of comparative studies on breastfeeding and non-breastfeeding for post-breast cancer patients. Some data show that 30% of post-breast cancer patients can lactate successfully with no impact on prognosis. The operationalization of breastfeeding is also a challenge for post-breast cancer patients. For example, the adequacy of breastfeeding from one breast, but most surveys have found that mothers are highly motivated to breastfeed. Patients who have had breast radiation after breast conservation have been found to report a high success rate of breastfeeding on their own. Rather than discouraging patients from breastfeeding at this stage, physicians should remind patients not to use medications indiscriminately so that they do not affect the baby via the breast milk. Individualized treatment of young breast cancer patients to accommodate the combined needs and considerations of the patient, family and disease is a challenge for physicians specializing in breast cancer. Multidisciplinary collaboration is also increasingly important. The above ideas are derived from previous retrospective studies and the data may be inadequate. There is also no separate cohort of hormone receptor positive and negative patients in the study. There is no final and definitive answer regarding the safety of pregnancy after breast cancer. This is a question that the International Breast Cancer Collaborative Group is conducting prospective clinical studies to answer. I believe that the issue of fertility after breast cancer should be studied early and with more attention because of the high proportion of young breast cancer patients in China and the possibility that in the near future, more young breast cancer patients will be only girls.