TV tonight: 'Broke Girls,' Bieber roast

2 Broke Girls

CBS, 8 ET/PT

Sandra Bernhard guest stars, which sets up one of those tough-choice situations for her fans. The good news, obviously, is she's on TV. The bad news is that Girls can't be counted on to make any better use of her than it makes of its regular cast — and that's very bad news, indeed.

Ken Burns Presents Cancer: The Emperor of All Maladies, A Film by Barak Goodman

PBS, 9 ET/PT (times may vary)

Produced and co-written by television-treasure Ken Burns, and directed by Barak Goodman, this moving three-night adaptation of Siddhartha Mukherjee's Pulitzer Prize-winning book traces the history of cancer from our first known encounters to our most recent efforts against it. But this is no academic exercise; it's a very human, sometimes very intimate story of our struggle to understand the disease and withstand its devastating assault. Despair and loss are part of the story, but so are salvation and hope — along with essential lessons about the resilience of the human spirit, the value of science and the scientific method, and the necessity of facing our fears and fighting back. It's a tough subject, but we can't conquer cancer by looking away.

The Comedy Central Roast Of Justin Bieber

Comedy, 10 ET/PT

Odds are if you like Bieber, this will seem too mean. And if you don't, it won't seem mean enough.