No I dont think so, you can use UMDGEN and open the ISO and save it as a cso file or open CSO file in UMDGEN and save it to ISO. When finished importing save it as CSO again in UMDGEN.
if i can say my opinion about it..CSO format save space,it's right..but gives some problems in playing the game ..i used a cso conversion for my modded GTA liberty city ,but i hated it's lost fluidity