I can see how it might sound confusing. I think it means that out of all the sorts of individual (i.e. treatment given personally to someone) treatments that could be given, e.g. drugs, operations, etc., these should be limited to supportive therapy only.
Supportive therapy is not new. It's any sort of treatment intended to relieve symptoms or help someone live with them rather than trying to make physiological changes to the patient.
Does that help?