Cancer (search) returned to a 13-year-old girl because her parents fought to prevent continuing treatment, the girl's former doctor testified Wednesday at a custody hearing.

Katie Wernecke (search) has been in foster care since June 4, when Nueces County sheriff's officials took her from a family ranch where she had been hiding with her mother.

Child Protective Services (search) officials took custody after doctors told them that the girl's parents were risking her life by refusing radiation therapy for Hodgkin's disease, a type of cancer that involves the lymph nodes.

Dr. Nejemie Alter diagnosed Katie's illness after she was taken to an emergency room in January with what her parents thought was pneumonia. Alter became her regular doctor but later ended the relationship because of extensive media coverage.

The Werneckes believed that four rounds of chemotherapy had destroyed the cancer. Edward Wernecke, Katie's father, told The Associated Press he feared the radiation treatment would put the teen at a heightened risk for breast cancer, stunt her growth and cause learning problems.

But Atler said Wednesday the delay in continuing treatment caused Katie's cancer to return. Testifying for the state, Alter also said he was concerned that the family didn't fill a prescription for an antibiotic.

The hearing was expected to conclude Wednesday afternoon.

Katie's parents resisted further treatment until they learned at another hearing Friday that a scan taken that day showed the cancer had returned. The parents agreed to allow the girl to undergo chemotherapy as they seek to regain custody.

Juvenile Court Judge Carl Lewis said it was clear to him Katie should remain in state custody, and that treatment must begin as soon as possible.

Peter Johnston, president of the Texas Center for Family Rights, said he was concerned about the way the state had stepped in.

"In this particular case the state alleges medical neglect. Katie's parents, however, have shown considerable interest in the well-being of their daughter," he said. "It seems to be typical of CPS's aggressive attack on families."

CPS spokesman Darrel Azar did not immediately return a call for comment but has said it is the state's role to step in when a matter is life-threatening.