Obese teens and young adults with leukemia are more likely to have a persistent residual disease compared to non-obese patients, according to a recent study.

Researchers from the Children's Hospital Los Angeles Saban Research Institute found that following induction chemotherapy, obese patients with acute lymphoblastic leukemia (ALL) were more than twice as likely to have minimal residual disease, in which residual leukemia cells cannot be seen under microscope but can be detected by more sensitive methods, it is among the strongest predictors of long-term survival and disease recurrence, compared to their lean counterparts.

"Induction chemotherapy provides a patient's best chance for remission or a cure," Steve Mittelman, principal investigator of the study, said in a statement. "Our findings indicate that a patient's obesity negatively impacts the ability of chemotherapy to kill leukemia cells, reducing the odds of survival."

For the study, researchers looked at nearly 200 patients diagnosed with ALL and between the ages of 1 and 21 years. They examined these patients to determine if body mass index (BMI) impacted response to initial chemotherapy. This response to initial chemotherapy (or induction therapy) is measured by the absence of leukemia cells in the bone marrow.

The minimal residual disease was determined by testing of bone marrow specimens taken at the end of induction therapy, and patients were followed for two to five years from the time of diagnosis.

Researchers found that lean patients with minimal residual disease had similar outcomes to obese patients without evidence of residual disease. Obese patients with residual disease had the worst outcomes. Additionally, although nearly a quarter of the patients initially deemed "lean" gained weight and become obese during the first month of treatment, these patients still showed similar outcomes to those who remained lean.

"In addition to increasing a patient's likelihood of having persistent disease following treatment, obesity appears to add a risk factor that changes the interaction between chemotherapy and residual leukemia cells," Hisham Abdel-Azim, co-lead investigator on the study, said in a statement.

Results from this study offer new avenues for investigation that include modifying chemotherapy regimens for obese patients and working to change a patient's weight status beginning at the time of diagnosis.

The findings were published in the journal Blood.