I don't see that there is in English. In German there is Epikur, Brief an Menoikeus : Edition, Übersetzung, Einleitung und Kommentar, by an Erik Hessler. In English it seems there is no commentary, but you might want to look at several works that probably treat the letter, e.g., Tim O'Keefe, Epicurus on Freedom or Jeffrey Fish and Kirk Sanders (eds.), Epicurus and the Epicurean Tradition.
Many many thanks. According to the extract of a review printed in Classical World (Summer 2015), this is exactly the kind of book I was looking for. If you ever encounter works in French or Italian similar to the one by Hessler, please let me know. Thanks also for the other references.
I found one in Italian (and Greek) online and downloaded a pdf. Edited & translated with notes by Graziano Arigghetti (Einaudi 1960). Easily findable :)