The Cochrane Collaboration: https://www.cochrane.org/
The Cochrane Collaboration is an international non-profit and independent organisation, dedicated to making up-to-date, accurate information about the effects of healthcare readily available worldwide. It produces and disseminates systematic reviews of healthcare interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. The Cochrane Collaboration was founded in 1993 and named for the British epidemiologist, Archie Cochrane. 

A guide for newcomers to The Cochrane Collaboration: https://www.cochrane.org/docs/newcomersguide.htm
The guide for newcomers includes information about the Cochrane Collaboration, systematic reviews and ways in which you can get involved.

Cochrane Collaboration Consumer Network: https://consumers.cochrane.org/ 
CCNet is the Cochrane Collaboration's Consumer Network. The network is made up of fellow consumers who are committed to the philosophies of The Cochrane Collaboration and the importance of consumer participation in informed healthcare decision-making processes. This website tells you about the role of health consumers, patients and the general public in the work of the Cochrane Collaboration. CCNet can link you with people who share your interests and connect you to the Cochrane groups that work in the areas of health care that concern you most.

Cochrane Cancer Network: http://www.canet.org/
The Cochrane Cancer Network represents the cancer wing of the Cochrane Collaboration. The Cochrane Cancer Network aims to facilitate the preparation, maintenance and dissemination of Cochrane systematic reviews in cancer addressing the information needs of cancer patients, clinical practitioners and researchers.

Cochrane Collaboration awarded seat at World Health Assembly (WHA)
For more information, refer to https://www.cochrane.org/features/cochrane-collaboration-awarded-seat-world-health-assembly

Disclaimer: The Cochrane Breast Cancer Group does not endorse the quality of the information on the above mentioned internet sites. These links are here only because they may be of interest to you.