Matt Sayles / Invision/AP 1 / 3
Matt Sayles / Invision/AP 1 / 3

NEW YORK (AP) -- Maura Tierney says she is dropping out of the new NBC series "Parenthood" to continue treatment for breast cancer.

In a statement Thursday, she expressed disappointment at not being part of the show, but said she and her doctors are confident about the outcome of her treatment.

Tierney had filmed the pilot episode for the series, but in July she was sidelined after a tumor was found in her breast. Production never resumed.

Another new series, the medical drama "Mercy," will premiere this fall instead.

"Parenthood," based on the 1989 movie that starred Steve Martin, will debut midseason, with Tierney's role expected to be recast.