Scrum has been successfully used for projects with 500+ team members lots of time. As SCRUM can only last for 15 minutes and some other similar rules hence in order to scale the SCRUM for bigger team we can use SCRUM OF SCRUMS. Based on the type of work the scrum team is constituted for every 7 to 10 team members having a Scrum master and the Product Owner. After the first lever team SCRUMS we have SCRUM of SCRUMS and there could also be more level of SCRUM OF SCRUMS.  Please read an excellent article on Scaling Scrums at Scrum Alliance

The scrum of scrums meetings can be scaled indefinitely through multiple layers.