Assume that ρ is a convex modular satisfying the -type condition and the modular space is either α-uniformly ρ-noncompact convex or it satisfies the strong Opial condition. We prove that the fixed point set of a commuting family of asymptotically non-expansive mappings defined from a ρ-convex weakly compact set C into C is a non-empty nonexpansive retract of C. We show that our results about existence of fixed point for commuting families of nonexpansive mappings also work if we replace the weak topology by some other topologies weaker than the ρ-topology. In particular, we can obtain fixed point results when C is ρ-a.e. compact in a modular function space.