Photo by Chad McNeeley
Based on results of a prospective study, investigators are advocating sequential minimal residual disease (MRD) monitoring in pediatric patients with acute lymphoblastic leukemia (ALL) who have detectable MRD after remission induction therapy.
The researchers said their findings show that MRD levels during remission induction treatment have important therapeutic indications, even in the context of MRD-guided therapy, as patients with higher MRD levels have worse outcomes.
Ching-Hon Pui, MD, of St. Jude Children’s Research Hospital in Memphis, Tennessee, and his colleagues described the findings in The Lancet Oncology.
The team analyzed 498 pediatric patients newly diagnosed with ALL, 492 of whom (99%) attained a complete remission following induction therapy and 491 of whom were monitored for MRD.
The researchers first estimated patients’ risk of relapse according to baseline clinical and laboratory features, provisionally classifying them as having a low, standard, or high risk of relapse.
But the investigators also took MRD levels into consideration. They measured MRD on days 19 and 46 of remission induction, on week 7 of maintenance treatment, and on weeks 17, 48, and 120 (the end of treatment).
The team found that 10-year event-free survival (EFS) was significantly worse for patients with 1% or greater MRD levels on day 19, regardless of their initial risk assessment. Ten-year EFS was 64.1% in these patients, compared to 90.7% in patients with lower or no detectable MRD (P<0.001).
Thirteen percent of patients who were deemed low-risk initially and 28% of patients deemed standard-risk initially had 1% or higher MRD levels on day 19. And these levels were associated with worse 10-year EFS.
In the provisional low-risk group, EFS was 69.2% in the high-MRD patients and 95.5% in the low-MRD patients (P<0.001). And in the provisional standard-risk group, 10-year EFS was 65.1% and 82.9%, respectively (P=0.01).
MRD levels at day 46 also appeared to have a bearing on EFS. For patients in the provisional low-risk group who had 1% or higher MRD on day 19 but became MRD-negative on day 46, 10-year EFS was 88.9%, compared to 59.2% for other provisionally low-risk patients who had detectable MRD on day 46 (P=0.02).
MRD levels on days 19 and 46 led to the reclassification of 50 patients from low-risk to a higher risk group that warranted more intensive therapy. The researchers credited the change with boosting survival.
“This analysis shows that MRD-directed therapy clearly contributed to the unprecedented high rates of long-term survival that patients in this study achieved,” Dr Pui said. “MRD proved to be a powerful way to identify high-risk patients who needed more intensive therapy and helped us avoid over-treatment of low-risk patients by reducing their exposure to chemotherapy.”
Still, MRD assessments at days 19 and 46 were not perfect predictors of patient outcomes. Of the patients who were MRD negative after remission induction, MRD re-emerged in 6 patients—4 of the 382 patients studied on week 7, 1 of the 448 studied at week 17, and 1 of the 437 studied at week 48. All but 1 of these patients died despite additional treatment.
On the other hand, relapse occurred in 2 of the 11 patients who had decreasing MRD levels between the end of induction and week 7 of maintenance therapy and were treated with chemotherapy alone.
Taking these results together, the investigators concluded that measuring MRD at days 19 and 46 was sufficient to guide the treatment of most pediatric ALL patients. However, MRD measurements should continue to guide treatment for patients with detectable MRD on day 46.
