Not sure but we have an image of the 1930 title page inscribed by Eliot at http://www.catholicvote.org/discuss/index.php?p=14958  and Gallup's Eliot bibliography (A15) has the hyphen. The poem as it stands now was originally published in 1930 as a book and so the title could in quotes or italicized. I prefer the quotes but I'm going to revert the article so it is italicized simply because it is easier.