A temporary leave of absence has turned into a complete exit for Maura Tierney.

The ER star had originally been scheduled to appear this fall in a new NBC show titled Parenthood. But when a tumor was discovered in one of her breasts, the series was pushed to the mid-season calendar to accommodate Tierney’s medical evaluations. Unfortunately, it appears Maura will need further treatment.

The actress’ rep announced the news through a statement today:

“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.  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 [executive producer] Jason Katims and NBC for their patience and support.”

No word at this time how this may affect the show’s rescheduled premiere date.