Dear Maintainer,

one cannot build 3DSlicer with the ITK shipped by Debian, because the ITK modules IOScanco, MGHIO, and GrowCut are
not installed with the package even if they are set to ON while building.
It could be a side effect of the flag -DITK_FORBID_DOWNLOADS=ON. If the buildd does not allow Internet connection,
I would suggest to create a patch on Debian side that adds the downloaded code into the repo as hard-coded module.
It seems that upstream already did that hard-coding a couple of months ago, so maybe it's just a matter of
backporting those changes.

Alternatively, to create a separate Debian package for each of
https://github.com/InsightSoftwareConsortium/ITKGrowCut
https://github.com/InsightSoftwareConsortium/itkMGHImageIO
https://github.com/InsightSoftwareConsortium/ITKIOScanco/

that one can apt-get install insighttoolkit-growcut etc.