Maura Tierney has pulled out of her new show to receive breast cancer treatment.

The "ER" actress - who played Dr. Abby Lockhart in the US medical drama – can't fit filming of the NBC series "Parenthood" around her treatment.

Her spokesman said: "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.

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"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."

The broadcasting network also released a statement saying they were "saddened" the 44-year-old star could not continue and wished her a full and speedy recovery.

"Parenthood" - which is based on the 1989 comedy film about a dysfunctional family - was due to start filming in July, but shooting was pushed back when Maura discovered a tumor in her breast.

It had been due to air this month, but no new date has been set.