Objective To systematically review the association between menstrual condition and the risk of breast cancer. Methods We searched The Cochrane Library (Issue 4, 2016), PubMed, EMbase, CNKI, WanFang Data, VIP and ScienceDirect databases from inception to June 1st 2016 to collect case-control studies about the association between menstrual condition and breast cancer. Two reviewers independently screened literature, extracted data and assessed the risk of bias of included studies. Then, meta-analysis was performed using Stata12.0 software. Results Eighty-three studies involving 48 811 breast cancer patients and 57 268 controls were finally included. The results of meta-analysis showed that breast cancer was associated with age at menarche≤13 years old (OR=1.17, 95%CI 1.12 to 1.24) and irregular menstruation (OR=1.98, 95%CI 1.62 to 2.41), but was not associated with history of dysmenorrhea, cycle time≥30 days and period of time>7 days. Further subgroup analysis showed that the sample size was one of the main source of heterogeneity for history of dysmenorrheal analysis, and breast cancer was associated with the history of dysmenorrhea after removing small-sampled studies (OR=1.47, 95%CI 1.36 to 1.59). The association between breast cancer and age at menarche≤13 years old, irregular menstruation was statistically significant in community control, but not in hospital control. The association between breast cancer and age at menarche≤13 years old, irregular menstruation were statistically significant both in Chinese and foreign population. Conclusion Early age at menarche, irregular menstruation and history of dysmenorrhea may be risk factors of breast cancer. Due to the limitation of quality and quanity of included studies, the above conclusions need more researches to verify.
Breast cancer is one of the most common malignant tumors in women. The systematic therapy of breast cancer may affect the endometrium and ovarian function, such as abnormal endometrial hyperplasia and abnormal uterine bleeding caused by ovulation disorders. If we do not consider the patients suffering from breast cancer, we can use progesterone drugs to stop bleeding, regulate menstruation, and protect the endometrium. But there is no consistent conclusion on the safety of progesterone drugs in breast cancer patients. This article reviews the security of progesterone drugs in breast cancer survivors from the perspective of basic and clinical research. At present, whether the use of progesterone drugs in breast cancer survivors increases the risk of disease may be related to the type, dosage, and method of use of progesterone drugs. At the same time, it is also related to the type of breast cancer the patient has. Based on the available data, it is safe to use natural progesterone or dydrogesterone for the short term in patients with breast cancer. More studies are needed to evaluate other approaches.