Since the subject of clinical data copies and/or links came up again, I was reminded of this old paper from the TCIA folks:
http://ceur-ws.org/Vol-2285/ICBO_2018_paper_37.pdf
and a related poster:
To make sure that those reading the post above are up to date in terms of IDC clinical data support capabilities, check out this thread to find notebooks demonstrating how to access and search clinical data using either pandas dataframe interface or SQL: New tutorial notebook: working with clinical data in IDC.