Do Sentinel 2 Level-1C images need atmospherical correction before EVI calculations?

I would like to use Sentinel-2 Level 1C images to produce EVI maps using the following equation :

EVI=G×(ρnir-ρred)/(ρnir+(C1×ρred-C2×ρblue )+L)

Can I use the Level 1C image as it is, or should I perform atmospheric correction first?

Because EVI is supposed to be an atmospheric resistant index using the coefficent C1 and C2, I’m not too sure if atmospheric correction is necessary or not. My images, from a semi-arid area, are mostly cloud free.