Photo courtesy of ASH
ORLANDO, FL—A subgroup of young patients with high-risk B-cell acute lymphoblastic leukemia (B-ALL) can have “outstanding outcomes” with contemporary therapy, according to researchers.
Results of a large study suggested that patients ages 1 to 30 who have high-risk B-ALL according to National Cancer Institute (NCI) classification can have high rates of event-free survival (EFS) and overall survival (OS) if they have favorable cytogenetic features, have no evidence of CNS disease, and have rapid minimal residual disease (MRD) responses.
The research suggested these patients will not benefit from further chemotherapy intensification.
Elizabeth Raetz, MD, of the University of Utah in Salt Lake City, presented these results at the 2015 ASH Annual Meeting (abstract 807).
She and her colleagues analyzed patients enrolled on the Children’s Oncology Group (COG) AALL03B1 classification study at the time of B-ALL diagnosis. From December 2003 to September 2011, there were 11,144 eligible patients enrolled on this trial.
Eighty-nine percent of these patients were also enrolled on a frontline ALL therapeutic trial, and 96% of these patients were evaluable for post-induction treatment assignment. Sixty-five percent of these patients were treated on a trial for NCI standard-risk B-ALL (COG-AALL0331), and 35% were treated on a trial for high-risk B-ALL (COG-AALL0232).
At the end of induction therapy, patients were classified into low-risk (29%), standard-risk (33%), high-risk (34%), and very-high-risk (4%) groups for further treatment allocation. The variables used for risk classification were age, initial white blood cell count, extramedullary disease status, blast cytogenetics, and early treatment response based on bone marrow morphology and day 29 MRD.
Patients with very-high-risk features (BCR-ABL1, hypodiploidy, induction failure, or poor response at day 43) did not continue on AALL0232/AALL0331 post-induction but did have outcome data captured for analysis.
Response and survival
Rapid early response was defined as M1 (<5% blasts) bone marrow by day 15 plus flow cytometry-based MRD <0.1% on day 29 of induction. Patients with either M2/M3 (≥5% blasts) day 15 marrow or MRD ≥0.1% at day 29 were deemed slow early responders.
Eighty-four percent of patients had a rapid early response to induction, and 16% had a slow early response.
For rapid early responders, the 5-year EFS was 89.3%, and the 5-year OS was 95.2%. For slow early responders, the EFS and OS rates were 67.9% and 84.3%, respectively (P<0.0001 for both EFS and OS comparisons).
Survival according to cytogenetics
Having favorable cytogenetic abnormalities (triple trisomies of chromosomes 4, 10, and 17 or ETV6-RUNX1 fusion) was associated with significantly better EFS and OS than having unfavorable cytogenetics (hypodiploidy [DNA index <0.81 or chromosomes < 44], MLL rearrangements, BCR-ABL1, or iAMP21).
And Dr Raetz pointed out that the 5-year OS exceeded 98% for patients with either standard- or high-risk disease who had favorable cytogenetics.
For patients who were ETV6-RUNX1-positive, the EFS was 93.2% and the OS was 98.3%. For patients who were ETV6-RUNX1 negative, the rates were 83.5% and 92%, respectively (P<0.0001).
For patients with triple trisomy, EFS was 94.7% and OS was 98.7%. For those without triple trisomy, the rates were 83.6% and 92.2%, respectively (P<0.0001).
For patients with MLL rearrangement, the EFS was 73.9% and the OS was 83.1%. For patients without MLL rearrangement, the rates were 85.9% and 93.6%, respectively (P<0.0001).
For patients who were positive for iAMP21, the EFS was 69.5% and the OS was 90.1%. For iAMP21-negative patients, the rates were 86.1% and 93.4%, respectively (P<0.0001 for PFS comparison and P=0.0026 for OS comparison).
Survival according to risk group and MRD
The researchers also assessed EFS and OS among patients with favorable cytogenetics according to NCI risk group and MRD at days 8 and 29.
“One thing to point out is that, regardless of having favorable cytogenetics, those individuals who had end-induction MRD values of greater than 0.01% had inferior outcomes, so that was still a prognostic marker,” Dr Raetz said.
“And one thing that we were pleasantly surprised to see was that, among the NCI high-risk patients, those who had very rapid MRD responses—so less than 1% at day 8 in the blood and less than 0.01% in the marrow on day 29—had a 94.9% 5-year event-free survival and 98.1% overall survival.”
The researchers also divided this group according to age—patients younger than 10 and those 10 years or older. There was no significant difference in EFS or OS between the age groups (P=0.126 and P=0.411).
Among patients with <1% MRD on day 8 and <0.01% MRD on day 29, the EFS was 95.7% and the OS was 99.1%.
Among patients with ≥1% MRD on day 8 and <0.01% MRD on day 29, the EFS was 91.7% and the OS was 99.4%.
Among patients with any MRD on day 8 and ≥0.01% MRD on day 29, the EFS was 88.1% and the OS was 96.8%.
Among patients with <1% MRD on day 8 and <0.01% MRD on day 29, the EFS was 94.9% and the OS was 98.1%.
Among patients with ≥1% MRD on day 8 and <0.01% MRD on day 29, the EFS was 93.6% and the OS was 95.5%.
Among patients with any MRD on day 8 and ≥0.01% MRD on day 29, the EFS was 75.4% and the OS was 90.4%.
In closing, Dr Raetz said this study showed that real‐time classification incorporating clinical features, blast cytogenetics, and early response was feasible in a large group of patients enrolled on COG ALL trials and identified patients with varying outcomes for risk‐based treatment allocation.
She noted that early response by marrow morphology was not prognostic when MRD response was used and is therefore no longer used in COG studies.
And although favorable cytogenetic features were not prognostic in NCI high-risk B‐ALL patients in prior COG studies, the current study indicates that these patients can have “excellent outcomes” if they have no evidence of CNS leukemia and are rapid MRD responders. So these patients will not benefit from further chemotherapy intensification.