It's unequivocal that screening reduces breast-cancer specific mortality. None of the studies are powered enough to draw a positive or negative conclusion for overall mortality. The second last link is an explanation of why this is the case, where we're at and what the implications are.

The last link explains the NCCN rationale and decision making process.

http://www.aapec.org/images/b69a380d-519a-415b-8e8c-8e7f2b02...

https://www.nejm.org/doi/full/10.1056/nejmoa1000727

https://academic.oup.com/jnci/article/106/11/dju261/1496367?...

https://www.bmj.com/content/bmj/352/bmj.h6080.full.pdf

https://jnccn.org/view/journals/jnccn/16/11/article-p1398.xm...