Ching-Hon Pui, MD

Sifting Needles from Haystacks

First, St. Jude pioneered a test that could pinpoint one leukemia cell among 10,000 normal cells. Now that test is helping guide therapy—with spectacular results.

One of the challenges in treating cancer is figuring out how intense the treatment should be for a patient.

A team led by Ching-Hon Pui, MD, Oncology chair at St. Jude Children’s Research Hospital, recently demonstrated that measuring the number of leukemia cells in patient bone marrow early in treatment can help determine how intense the chemotherapy needs to be for patients with acute lymphoblastic leukemia (ALL).

“This is the most powerful way to identify high-risk patients who need more intensive therapy. It also helps us avoid over-treating low-risk patients,” Pui explains.

The procedure evaluates a patient’s response to treatment. The test measures minimal residual disease (MRD)—the number of leukemia cells that remain during and after the first phase of treatment, which is called remission induction therapy. MRD testing is done on the 19th and 46th days of induction treatment when, Pui says, “we can identify patients who will have very, very good treatment outcomes without intensive therapy.”

Those patients can receive low-intensity therapy, which lowers the risks of treatment-related side effects.

Children with higher MRD results require more intensive therapy for cures. Thanks in part to this method, 94 percent of children with ALL survive their disease.

St. Jude is the first hospital to pioneer the use of MRD to help guide treatment. 

Sweet remission

A St. Jude study about MRD published in the journal Lancet Oncology showed that MRD testing twice, instead of multiple times during the 2.5 years of treatment, was enough to guide therapy. Not only does that save money, but it also helps children avoid the discomfort and risk of repeated bone marrow aspirations.

The MRD test can detect even one leukemia cell among 10,000 normal cells. But that’s not good enough for Pui and his team.

They plan to further fine-tune the test, so that hospitals worldwide can use it to separate high-risk patients from those who can be cured with lower levels of treatment. Pui and his colleagues hope the use of MRD tests can also extend beyond children to adults.

“Research is needed to determine if even more sensitive methods of MRD measurement can improve our precision in predicting outcomes,” Pui says. “It is also important to develop simple methods that maintain or increase the reliability and can be readily extended to all laboratories and, hence, all patients.” 

Reprinted from Promise, Summer 2015

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