A teenage girl who was ordered by a court to undergo chemotherapy has seen her illness go into remission.

The Connecticut Department of Children and Families (DCF) said on Sunday that the teenager, who is identified in court documents only as Cassandra C, was making a recovery that was better than expected after she was confined to hospital and mandated to receive chemotherapy.

The 17-year-old was given a diagnosis of Hodgkin’s lymphoma last September. After initial surgery failed, she was given two rounds of chemotherapy. She then asked for treatment to be stopped and, in order to avoid further trips to hospital, ran away from home.

The girl’s mother supported her choice but the DCF claimed custody of the girl and took the case to court, arguing that it had a responsibility to treat her after doctors said the cancer would almost certainly kill her without chemotherapy.

“We are very pleased with Cassandra’s progress toward a complete recovery. We have had full confidence throughout that the medical professionals involved in her treatment would be successful in saving her life,” said Joette Katz, the state DCF commissioner.

Cassandra will turn 18 in September, and will then be free to make her own medical decisions. Unlike several other states, Connecticut does not have a “mature minor” law that allows children aged 16 or 17 and deemed sufficiently responsible to decide on their medical treatment. Such laws are usually used when a child disagrees with his or her parents over treatment.

Cassandra’s mother, Jackie Fortin of Windsor Locks, Connecticut, said during the row over treatment that she and her daughter had simply sought the right to pursue alternative medicine rather than allowing the hospital to mandate chemotherapy, which they likened to putting “poison” in her body without her permission.

The Connecticut supreme court ruled last week that state officials were not violating Cassandra’s rights by forcing her to undergo the hospital’s chosen treatment.

After Cassandra refused to undergo further treatment last September, the DCF investigated and a trial court granted it temporary custody of the teen. Lawyers for Cassandra and her mother sought an injunction prohibiting medical treatment but were unsuccessful. She underwent two days of treatment in November but ran away for a week, according to court documents.

Cassandra’s treatment resumed on 17 December, with surgery to install a port in her chest. Chemotherapy began the next day and continues. She is confined in a room at Connecticut Children’s Medical Center, in Hartford.

“Whether I live 17 years or 100 years should not be anyone’s choice but mine,” the girl wrote in an article for the Hartford Courant. “How long is a person actually supposed to live and why? Who determines that? I care about the quality of my life, not just the quantity.”

The girl was appointed a lawyer by the court, assistant public defender Joshua Michtom.

“One has a right to bodily integrity. It doesn’t matter if it’s harmful. An adult’s right to refuse care is without limitation, provided they’re not incompetent,” he said.

But the DCF argued that Cassandra’s illness was curable and the state had a responsibility to administer the treatment she needed to have the chance to become “a healthy, happy adult”. The highest court in the state agreed.