It's been a pretty amazing 12 months for Joseph Gordon-Levitt.  He starred in the summer breakout hit "500 Days of Summer," the blockbuster "G.I. Joe: The Rise of Cobra," shot Christopher Nolan's thriller "Inception" and was the saving grace of Sundance pickup "Hesher."  Now, Gordon-Levitt is stepping in at the last minute as the lead character in a new Jonathan Levine's new untitled cancer comedy.

Levitt is replacing James McAvoy who, according to distributor Summit Entertainment, had to drop out "due to unrelated circumstances beyond his control." Whether that really means "family matters" or he got sucked into another movie via contract is unclear.  At the moment, it is allowing Gordon-Levitt to join an intriguing cast including Best Supporting Actress nominee Anna Kendrick, Bryce Dallas Howard, Anjelica Huston, Philip Baker Hall and Seth Rogen. 

Based on screenwriter Will Reiser's true life story, the film follows a twentysomething man who discovers he has cancer.  Rogen is also producing.  In a statement to The Hollywood Reporter, Rogen reflected on McAvoy leaving saying, "It's incredibly unfortunate that circumstances outside of everyone's control have taken James away from the project, but, with James' blessing, we were able to have Joseph step in to take on the role of Adam.  We all look forward to working with James in the future."

McAvoy is scheduled to present at this Sunday's 82nd Academy Awards.

Production begins Monday in Vancouver.