The Medina Gazette reports Sarah Hershberger and her parents weren't at home in Homer Township during an Oct. 30 welfare check, and authorities haven't seen them since summer.
Last month, a court decided an attorney who is a registered nurse would have power to make medical decisions for the girl. That guardian's attorney says he isn't sure where the family is.
Doctors have said Sarah will die without chemotherapy.
Her parents say they stopped the treatments because the effects were terrible and opted for "natural" medicines. The Amish generally shun modern life.
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READ: Court sides with Ohio hospital on Amish girl care