Town Portal Scroll makes the caster invulnerable, is it posible to avoid this?

Hey, im using Town Portal Scroll with a cast time of 5 seconds to alow players to teleport away from battle, the problem is that if that player was about to die and he starts casting the spell he stop being attacked, which makes the game very cheap (its an AOS so heros are supposed to die) so im wondering if theres a way to alow the player to cast but at the same time if hes attacked spell should stop, the biggest issue with this spell is that the unit becomes invulnerable from the moment it starts casting.

Any suggestions? should I change the spell?

Thanks!

Perhaps you could try basing it on Archmage's Mass Teleport rather than Town Portal?

Certainly is possible.

or you could do this....