Part of the description of forcecage states:
A prison in the shape of a box can be up to 10 feet on a side, creating a solid barrier that prevents any matter from passing through it and blocking any spells cast into or out from the area.
If forcecage is cast (in the form of a 10-foot solid box) on a point where an existing spell like sickening radiance is centered, does it break the concentration of the previously cast area-of-effect spell? Or would it trap the AoE effect inside the box?