SLEEPY EYE, Minnesota (CNN) -- The father of a cancer-stricken 13-year-old boy whose mother has fled with him to keep him from undergoing chemotherapy appealed Thursday for her to bring him home.
Doctors say Daniel Hauser's lymphoma responded well to a first round of chemotherapy in February.
"Please bring Danny home so that we can decide as a family what Danny's treatment should be," Anthony Hauser said, directing his halting comments to his wife, Colleen, as he stood in front of television cameras outside the family's house.
"I know you're scared and I feel that you left out of fear, maybe without thinking it all the way through," he continued. "Danny is my son and the rest of the family is worried sick about Danny, how he is and how he's going to come out.
"Please call me and let's talk about how you can come back here and we can get this worked out, what's best for Danny."
The boy was diagnosed with Stage 2B Hodgkin's lymphoma in January. The next month, he received a single course of treatment, which succeeded in shrinking a tumor in his chest but caused side effects that upset the family, doctors have said. Watch father urge the pair to come back »
Dr. Bruce Bostrom, the cancer specialist who oversaw that course of chemotherapy, told KARE-TV in Minneapolis that, without further treatment, Daniel's odds of survival would plummet from 80 to 90 percent to about 5 percent.
Daniel's second round of treatment was to have begun March 5, said the pediatric oncologist and associate professor at the University of Minnesota Medical School.
In April, after the boy had not returned for the second course, Bostrom called the family and left a message threatening to report them for child neglect, he said.
Colleen Hauser returned his call, telling him she was seeking a second opinion. But the doctor who ultimately cared for the boy has said he was only treating his symptoms, not the cancer itself, Bostrom said.
So Bostrom reported the family to authorities, the first time he has taken such a step in 25 years of practice, he said.
"I think it's our and my duty to do this," he said.
Meanwhile, the opportunity to intervene is narrowing. "He's now almost three months late, that's why it has regrown," Bostrom said, referring to another doctor's interpretation of a chest X-ray that showed Monday the tumor had worsened.
"It means his cancer is back and he is in danger," Bostrom said. "It could block his airway; he could develop life-threatening breathing problems and possibly even die from it. It could be within a few weeks or a month at the most, I would say."
Hodgkin's lymphoma is a cancer of the immune system. Stage 2B refers to the two areas of the body where Daniel has it -- the chest and the neck -- and the symptoms he has experienced: tumor, fatigue, weight loss and night sweats.
Authorities said Wednesday that Colleen and Daniel Hauser were near Los Angeles, California, perhaps en route to Mexico for more holistic treatment of his lymphoma.
Brown County, Minnesota, Sheriff Rich Offmann cited "reliable information" in making the announcement to reporters. The sheriff's office issued a felony arrest warrant for Colleen Hauser on Thursday in an effort to "ensure extradition to Minnesota."
Family spokesman Dan Zwakman said on Thursday that Anthony Hauser was not aware that his wife was taking the child.
"From all appearances," Zwakman said, "it was a case of her decision by herself." Watch what legal issues are at stake »
The boy and his mother were last reported seen Monday in Minnesota. When mother and son failed to show up at a court hearing Tuesday, Brown County District Judge John R. Rodenberg issued an arrest warrant for Colleen Hauser.
Court documents show that the doctors estimated the boy's chance of five-year remission with more chemotherapy and possibly radiation at 80 percent to 95 percent.
But the family rejected standard treatment, opting instead for a holistic medical treatment based on Native American healing practices called Nemenhah.
In a written statement issued last week, an attorney for the parents said they "believe that the injection of chemotherapy into Danny Hauser amounts to an assault upon his body, and torture when it occurs over a long period of time."
Dr. Sanjay Gupta, CNN chief medical correspondent, said he had no doubts about what to do.
"My advice would be to treat him, without question," he said. "He has a very, very good chance of surviving, being cured and never having to deal with this again. As a doctor, as a fellow citizen, I would say he should be treated." Watch Gupta discuss Daniel's chances »
But Zwakman told CNN's "American Morning" program Thursday that he knows five people who have been cured with natural healing.
"Yes, it's happened many times," he said. Watch Zwakman speak to CNN »
Mankato, Minnesota, lawyer Calvin P. Johnson, who identified himself as the Hauser family's attorney, said Thursday that forcing treatment would constitute "assault and torture."
Johnson said officials were forcing treatment neither the boy nor his parents want.
"Anthony and Colleen Hauser share Danny's viewpoint: They do not approve of chemotherapy. Under the circumstances of this case, chemotherapy constitutes assault and torture, when given to a young man who believes that it will kill him," Johnson said in a written statement.
CNN's Chris Welch contributed to this report.