An experimental cancer drug — in a single treatment — cured one-third of patients in a trial who had lymphoma, a type of blood cancer that begins in the lymph nodes. While the news is being called a breakthrough, researchers also caution that the same drug may have killed two other patients involved in the trial, and they say far more research is needed before the drug can be used as treatment.

The process involves using gene therapy to prompt patients' blood cells to attack cancer, and was developed by the private drug company Kite Pharma, The Independent reported. Eighty-two percent of patients saw their tumors shrink by half or more at some point in the study, and more than nine months later, one-third of patients treated showed no more signs of the blood cancer. In addition, more than half of the patients were still alive nine months after treatment, despite being expected to live for only six.

Read: Hodgkin's Disease Vs. Non-Hodgkin's Lymphoma: Early Symptoms And Survival Rates For Blood Cancers

“The numbers are fantastic,” Dr. Fred Locke, a blood cancer expert at Moffitt Cancer Centre in Tampa, Florida, who co-led the study and was a paid adviser to Kite Pharma, told The Independent. “These are heavily treated patients who have no other options.”

The outcome was not as successful for all of these patients, however. Of the 101 people involved in the study, two may have died as a direct result of this treatment, though all patients were terminally ill.

Although the results are exciting, the long-term effects of this treatment are unknown. In addition, we don't know if the lymphoma's remission is permanent, or if it will soon return. More research is needed, scientists say.

According to the American Cancer Society, Lymphoma cancer starts in immune system cells. The two main types of lymphoma are Hodgkin lymphoma and non-Hodgkin lymphoma (NHL), and both can occur in children and adults.

Currently, both treatment and survival chances both depend on the stage and type of lymphoma, The National Cancer Institute reports. A variety of treatment options exist for lymphoma patients, including immunology, chemotherapy, radiation therapy, and stem cell transplants.

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