Maura Tierney, who played nurse Abby Lockhart on NBC’s medical drama ER for a decade, is exiting the network’s new fall drama Parenthood as she continues to undergo treatment to battle breast cancer.

Maura’s role as Sarah, one of four adult children born to a pair of eccentric parents, will be recast, NBC confirmed on Thursday.

In July, NBC postponed production on the show for eight weeks to allow the actress time to undergo treatment.

“While we are saddened that Maura Tierney won’t be able to continue in her current role in Parenthood, our main concern is for her quick and full recovery. Our thoughts and best wishes are with her,” an NBC spokesperson said.

Although the show is moving on without her, a rep for Tierney says the actress’ prognosis is good.

“Maura Tierney regrets that she will not be able to continue her role on Parenthood due to a conflict with the production schedule of the show and her breast cancer treatments,” the actress’ rep said in a statement to PEOPLE. “Ms. Tierney and her doctors remain confident that the outcome of her treatments will be positive. She is deeply disappointed that she will not be able to rejoin such a highly respected, talented, fun and funny group of actors and wishes to thank Jason Katims and NBC for their patience and support.”