This is the 5546th most frequent Japanese word.
かねて
"かねて" means "previously" or "for some time."
かねてから is used here to express an action or desire that has been continuous from the past up to the present.
私はかねてから彼に事実を伝えたかった。
I had wanted to tell him the truth for some time.
かねて懸念されていた highlights a situation that has been persisting for a notable amount of time.
かねて懸念されていた問題が、ついに解決した。
The issue that had long been a concern has finally been resolved.
かねて計画していた indicates ongoing preparation or planning from the past to the current conclusion.