On Wednesday, a US study suggested that a cancer-killing therapy that engineers a patient's own immune cells for wiping out chronic lymphocytic leukemia (CLL) has displayed long-term success in a group of individuals.

According to experts, the approach is on the cutting edge of a growing field called immunotherapy. The therapy coaxes the body to kill off cancer. They said that it might revolutionize oncology someday by bringing the use of toxic chemotherapy to end.

The University of Pennsylvania's Abramson Cancer Center and Perelman School of Medicine developed the method, called CTL019, and reported the first long-term results on 14 initial patients.

The findings published in the journal Science Translational Medicine said that in the study, eight of the participating adults (57%) responded to the treatment. Four of whom went into long-term remission and the other four experienced a partial response.

The first person who received the treatment recently marked five years cancer-free, while two others made it to four and half years without any sign of cancer's return. The fourth once stayed in remission for 21 months, and then died due to an infection, received from a surgery unrelated to the leukemia.

A professor of immunotherapy in Penn's department of pathology and laboratory medicine Carl June, senior author, said, "Our tests of patients who experienced complete remissions showed that the modified cells remain in patients' bodies for years after their infusions, with no sign of cancerous or normal B cells".

Carl June said it has indicated that at least some of the CTL019 cells retained their ability to hunt for cancerous cells for very long time.