An earlier version of this editorial incorrectly referred to Kymriah as a drug. Krymriah is a treatment for acute lymphoblastic leukemia. Additionally, the editorial incorrectly stated that patients in “remission” may face revitalized cancer; the correct word was relapse. This version has been updated.

Emily Whitehead,12, with her father, Tom, and mother, Kari, in July in Philipsburg, Pa. Emily’s leukemia went into remission after she received an experimental treatment now known as Kymriah. (SEAN SIMMERS/For The Washington Post)

THE FOOD and Drug Administration approved a new treatment last month for acute lymphoblastic leukemia, an aggressive disorder of the blood and bone marrow that is the most common childhood cancer in the United States. On its face, this may not seem like big news. The government is approving it for use only on young people, only 3,100 of whom are diagnosed with the disease every year. So a relatively small number of Americans stands to benefit.

The reason everyone should pay attention is that this new treatment, Kymriah, might be only the first in a line of revolutionary new treatments. This could be "an inflection point in our ability to treat and even cure many intractable illnesses," FDA Commissioner Scott Gottlieb said, giving hope to patients who have advanced or recurrent cancer resistant to traditional therapies, as well as other serious illnesses.

Here's how the new treatment works: Specialists take a patient's immune cells and reprogram them with a new gene that instructs them to detect and kill specific cancer cells. They then inject those reprogrammed cells back into patients' bodies, where they go to work destroying deadly malignancies. In a clinical trial, 83 percent of patients saw remission within three months. A similar process has seen some success in treating metastatic melanoma, a diagnosis that typically amounts to a death sentence.

This technique is one of several classified as "gene therapies." Scientists are researching ways of deactivating or repairing faulty DNA within people's bodies, another pathway that could lead to breakthrough cures. It is not the only method doctors have used to rally patients' immune systems against cancers. Checkpoint inhibitors, which help the body's existing immune cells recognize cancers, have also shown much promise, including in treating former president Jimmy Carter's melanoma.

All that said, enthusiasm must remain checked. Gene therapies and other immunotherapies still do not work in many patients. In others, relapse may still occur, and their revitalized cancer may be even harder to treat. The process can also lead to horrible side effects as the immune-system enhancement wreaks its own havoc on the body. Reprogrammed immune agents will kill helpful cells as well as deadly ones. The FDA will require hospitals and clinics that want to offer Kymriah to be specially certified.

Then there is the cost — $475,000 per treatment. The sticker shock is only somewhat relieved by the fact that Kymriah involves only a single treatment per patient, and Novartis, its maker, has pledged to take payment only when the therapy works within the first month of treatment. British health officials, known for aggressively holding down pharmaceutical costs, concluded that the treatment's value could be pegged as high as $649,000. Axios's Bob Herman suggests that Novartis kept costs lower because it may be just the first in a line of new therapies to treat other types of cancer.

If that is so, there will be and should be more scrutiny paid to how these treatments are paid for. But it would nevertheless represent sorely needed progress in the war on one of humankind's principal adversaries.