NEW YORK  - The US edition of fashion magazine Vogue said its upcoming Sep issue will be its biggest ever, surpassing the previous record-setter made famous in a documentary. With pop diva Lady Gaga on the cover, the 916-page door stopper, scheduled to hit newsstands in the US on Aug 21, will mark the influential Conde Nast title’s 120th anniversary. “It is our biggest issue ever,” a spokeswoman said, although the fact is not trumpeted on a cover that promises “916 pages of spectacular fall fashion for all.” The Sep 2007 issue, with “840 pages of fashion ... Our Biggest Issue Ever,” was the focal point of director RJ Cutler’s 2009 fly-on-the-wall film documentary “The September Issue.”