Sam released a statement regarding the cancellation.
Here it is in its entirety:
This season's shows are as good as any we've ever made on Law & Order.
A job like the one I've had doesn't happen in my line of work. I've had a great time. It's opened countless opportunities, kept me close to home, family, and friends, given me millions of wonderful things to say in highly dramatic circumstances, and kept me out of trouble.
I have no complaints, none, but I'm as surprised as anyone. I couldn't imagine there would not be a 21st season on NBC, either. So, if we end up tied for first with "Gunsmoke" for longest running primetime drama ever, that'll do. No complaints.
I'm permanently grateful to Dick Wolf and the close-knit community that's our crew, writers, actors and producers. What a class act they are, and with NBC's support over these many years, they've changed my life.
To the fans of the show, thanks for your amazing loyalty. Last but not least, unbelievable numbers of people in New York adopted us as their mascot, the highest possible compliment from the best town around.