"The Bob Newhart Show" star and TV personality succumbed to lung cancer.

ET has confirmed that actress SUZANNE PLESHETTE passed away from lung cancer Saturday. The TV and Broadway star died at her Los Angeles home surrounded by family, her step-son JASON POSTON tells us. He describes it as a "quiet, elegant passing." She was 70 years old.

Last August, Pleshette told us she had just finished chemotherapy treatment for the cancer and was feeling "physically weak" but very "lucky." "I've had chemo but I haven't had any pain," she said. "It's almost like I go in for a spa treatment once a month ... but it's not as simple as that."

To TV audiences, she was probably best known as the no-nonsense wife of BOB NEWHART on "The Bob Newhart Show." Newhart commented to ET on Pleshette's passing: "Although we knew she was quite sick, she was one of those people that you thought would go on forever. If anyone could beat cancer, it was Suzy -- she was such an indomitable spirit. She was a pro's pro and I know she was looking forward to getting a star on the Hollywood Walk of Fame on her birthday Jan. 31."

Later in life, Pleshette married funnyman TOM POSTON, who played the eccentric George on the spinoff "Newhart." He died last year.

Pleshette has also guest-starred in episodes of "Will & Grace" and "8 Simple Rules ... For Dating My Teenage Daughter." Early in her career, she starred in films such as 'The Birds,' 'Rome Adventure' and the Disney comedies 'Blackbeard's Ghost' and 'The Adventures of Bullwhip Griffin.'