Well, Edo Tensei isn't phisical form, but just name for specific jutsu of reanimation. Reanimated Madara keapt alive becouse of Hashirama cell and not becouse someone casting Edo Tensei jutsu on him to keaping him alive trough chakra.

For exemple we can take Gaara, he is also reanimated by Chiyo, but he is never anything close to edo tensei