VDP upgrade from 5.1.11.3 to 5.5.6

Is it possible to upgrade vSphere Data Protection from 5.1.11.3 to 5.5.6 ??

In the VMware interoperability list, vCenter 5.1 shows as compatible with VDP 5.5.6, but in VDP administrators guide, there's no allowed upgrade path from VDP 5.1.11.3 to 5.5.6

Thanks!!