Making sense of Cadence schematic source files
I'm assuming you're talking about Cadence Allegro, or Orcad. Cadence has many other products used in VLSI and ASIC design that use different file conventions.

Back to your question, it might be a proprietary binary file, so it might not be possible to read that information unless you reverse engineer the database structure.

For example, the old Cadence Virtuoso used a proprietary database with extension .cdk, but recently moved to the open source .oa.