Remove lines containing only a word and a number ? (notepad++, regex)

I have several hundreds of .txt files from which I would like to remove the lines where only the word "Volume" followed by a number appears.
The word "Volume" may appear several times in each text file but I only want to delete the lines where the only text on that line is Volume and some number.

Example of line I want to be deleted:

                 Volume 158

Example of line I don't want to be deleted:

  text text text Volume 158 text text text

Please help me accomplish this using notepad++ ?