A groundbreaking cancer treatment that uses the body's own immune system to attack cancerous cells is likely to be approved by the Food and Drug Administration.

The treatment, called CAR-T cell immunotherapy could be approved as early as the end of September after a unanimous approval from the agency's Oncologic Drugs Advisory Committee.

Timothy Cripe, a panel member who is an oncologist with Nationwide Children's Hospital in Columbus, Ohio, told NPR the treatment the "most exciting thing I've seen in my lifetime."

The treatment takes immune system cells - known as T cells - from a patient's body and freezes them. Scientists then modify the genes in them so that they will only attack cancerous cells, multiply, and refreeze them.

They are then reintroduced into the patient's body to begin the process of multiplying to the millions and destroying the cancer, leaving behind healthy cells.

Since the patient's own cells are being used, some scientists call it a "living drug".

If approved it would be the first gene-based therapy approved by the government agency.

Previous attempts to harness a patient's own immune system in fighting cancerous cells have not had the success of CAR-T cell immunotherapy.

Pharmaceutical company Novartis is seeking approval of the treatment and Dr. David Lebwohl, head of the company's CAR-T Franchise Global Program, called it a "new hope for patients".

They estimate the whole treatment from "vein to vein" would be about 22 days.

The treatment is so far targeted towards helping children and young adults from three to 25 years old who have not responded to traditional treatments for their B cell acute lymphoblastic leukemia - about 600 patients a year. It is the most common type of childhood cancer in the US.

Novartis presented a study to the FDA of 63 patients in 11 countries that received the immunotherapy from April 2015 to August 2016. Over 82 per cent of them - or 52 patients - went into remission.

Despite the mostly positive results, the side effects can be deadly for some patients when vital organs are attacked by the modified T cells that are reintroduced into the body - called "cytokine release syndrome".

Novartis said some patients did experience fever, flulike symptoms, delirium, and seizures, but no fatal brain swelling.

Once approved, the company plans on limiting the therapy's availability to 30 to 35 medical centres with people who have had extensive company training with the treatment.

It also plans to have Novartis employees at hospitals using the therapy in order to follow patients for up to 15 years.

Some are concerned about the long-term effects of the treatment, which uses a virus to modify the T cells.

The FDA is not required to follow the committee's recommendation, but it is normal for them to do so.

No pricing information has been released by Novartis and the issue is out of the FDA's domain, but estimated costs range in the hundreds of thousands of dollars.

A public comment hearing was held at the FDA headquarters in Silver Spring, Maryland where several parents told stories about their children's positive experiences with CAR-T cell.