He doesn't have a source because it's not true.

https://www.charitynavigator.org/index.cfm?bay=search.summary&orgid=4509

In 2017, Susan G Komen foundation spent 78.9% of their total income on their actual charity programs. 11.1% went to fund-raising expenses, and 9.8% went to administrative expenses. That's pretty decent, IMO.

The only thing I could find about only 8% going to something is that 8% of their program expenses in 2015 went towards actual treatment of real women with breast cancer. The rest went to education, screening, and research.

I'm not saying Susan G Komen is the best breast cancer charity to donate to, but they're not as bad as people in this thread are saying.