Lenovo does not support eGPUs on P50 ThinkPads because testing revealed a dramatic drop in system performance.

In internal testing on a GeForce GTX 1080 card running on a P50 with Razer Core via Thunderbolt 3.0 (Gen3 x4 PCIe) versus a P510 in Gen3 x16 PCIe slot, Lenovo found dramatic performance losses. This loss is quantified as up to a 20% performance loss running standard CAD applications, with up to 65% performance loss running M&E applications like 3ds Max.

For this reason, eGPU on P50 ThinkPads will remain unsupported.