There's no cable that specifically runs down the back or down the chest.
The distance from the IEM to the "Y" joint will dictate where it can run. If the legs of the Y are shorter, you can't run the cable down your chest as it will catch on your throat. Such cables have to go down your back. Cables wtih longer legs to the "Y" can run down the chest. Before my X5s, I had UE TF10s. The OEM cable had a long enough "Y" that I could run it down my chest. A popular mod at the time was to put Westone cables on TF10s. I tried it, the Y was too short to clear my neck so the cable had to go down my back. As I mentioned, I don't like that so the OEM cable went back on.