The dramedy about a woman with terminal cancer usually airs in 30-minute installments. Season 3 had 10 episodes.
"From its inception, the show has been unique and we've found a creative way to bring conclusion to Cathy's story," E! News said Showtime Entertainment President David Nevins told reporters at the Television Critics Association press tour Monday.
"I wouldn't assume anything on how it's going to end," he said. "We've been having a lot of very interesting creative conversations on how to do it. It's very important with a premium network that shows be able to plan their end and do it the right way. They've got a very interesting and novel, and form-breaking way to handle where the show is going. I think it's going to make for a very interesting season."