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Flow cytometry versus morphology
Source: Childhood Acute Lymphoblastic Leukemia Treatment (PDQ®)–Health Professional Version, National Cancer Institute.
Source updated: April 21, 2025 · Captured 2026-09-09.
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MRD is now being integrated with morphological assessment into the response to induction therapy, on the basis of studies that showed that patients with MRD levels above 5%, despite morphological CR, had outcomes similar to patients with morphological induction failure.
In the UKALL2003 (NCT00222612) study, 59 of 3,113 patients (1.9%) had morphological induction failure.[153]
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In the UKALL2003 (NCT00222612) study, 59 of 3,113 patients (1.9%) had morphological induction failure.[153]
The 5-year EFS rate was 51%, and the OS rate was 58%.
In the UKALL2003 (NCT00222612) study, 59 of 3,113 patients (1.9%) had morphological induction failure.[153]
2.3% of patients had a morphological remission but had MRD of ≥5% measured by real-time quantitative IgH–T-cell receptor PCR. This group had a 5-year EFS rate of 47%, similar to those with morphological induction failure.
In the UKALL2003 (NCT00222612) study, 59 of 3,113 patients (1.9%) had morphological induction failure.[153]
The authors suggested that using both morphological and MRD criteria to define induction failure would more precisely identify patients with poor outcomes.
A study of 9,350 patients enrolled on COG clinical trials between 2004 and 2014 compared characteristics of patients and their outcomes categorized by morphology (M1 vs. M2/M3) and MRD status assessed by flow cytometry (<5% vs. ≥5%). Morphological remission (M1 status) was achieved for 98.6% of B-ALL patients and 93.8% of T-ALL patients at the EOI.[159]
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A study of 9,350 patients enrolled on COG clinical trials between 2004 and 2014 compared characteristics of patients and their outcomes categorized by morphology (M1 vs. M2/M3) and MRD status assessed by flow cytometry (<5% vs. ≥5%). Morphological remission (M1 status) was achieved for 98.6% of B-ALL patients and 93.8% of T-ALL patients at the EOI.[159]
Morphology and MRD were concordant in 97.4% of children. However, only 87.3% of T-ALL patients were M1 with MRD of <5%, while 97.8% of B-ALL patients were in concordant remission.
A study of 9,350 patients enrolled on COG clinical trials between 2004 and 2014 compared characteristics of patients and their outcomes categorized by morphology (M1 vs. M2/M3) and MRD status assessed by flow cytometry (<5% vs. ≥5%). Morphological remission (M1 status) was achieved for 98.6% of B-ALL patients and 93.8% of T-ALL patients at the EOI.[159]
Approximately 20% of patients (40 of 202) with M2/M3 morphology had MRD of <5%. B-ALL patients with M2/M3 morphology but MRD of <5% had a 5-year OS rate of 72.7%, which was inferior to that of patients concordantly in remission (5-year OS rate, 93.8%) but superior to that of patients with M3 marrow (5-year OS rate, 43.4%).
A study of 9,350 patients enrolled on COG clinical trials between 2004 and 2014 compared characteristics of patients and their outcomes categorized by morphology (M1 vs. M2/M3) and MRD status assessed by flow cytometry (<5% vs. ≥5%). Morphological remission (M1 status) was achieved for 98.6% of B-ALL patients and 93.8% of T-ALL patients at the EOI.[159]
Among B-ALL and T-ALL patients with M1 marrow, 0.9% of B-ALL patients and 6.9% of T-ALL patients had MRD of ≥5%. Their outcome was compared with that of patients with M1 marrow and MRD of <5% and are shown in Table 5 below.
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A study of 9,350 patients enrolled on COG clinical trials between 2004 and 2014 compared characteristics of patients and their outcomes categorized by morphology (M1 vs. M2/M3) and MRD status assessed by flow cytometry (<5% vs. ≥5%). Morphological remission (M1 status) was achieved for 98.6% of B-ALL patients and 93.8% of T-ALL patients at the EOI.[159]
Table 5 shows that for children with B-ALL with M1 marrow and MRD of ≥5%, the 5-year EFS rate was significantly inferior to that of children concordantly in remission (59.1% vs. 87.1%) but was superior to that of children concordantly not in remission (M2 with MRD ≥5%: 5-year EFS rate, 39.1%).
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A study of 9,350 patients enrolled on COG clinical trials between 2004 and 2014 compared characteristics of patients and their outcomes categorized by morphology (M1 vs. M2/M3) and MRD status assessed by flow cytometry (<5% vs. ≥5%). Morphological remission (M1 status) was achieved for 98.6% of B-ALL patients and 93.8% of T-ALL patients at the EOI.[159]
The impact on EFS for MRD of ≥5% for children with B-ALL in morphological remission was driven by NCI high-risk patients, as there was no significant difference in EFS between NCI standard-risk patients in morphological remission with or without MRD of ≥5%.
A study of 9,350 patients enrolled on COG clinical trials between 2004 and 2014 compared characteristics of patients and their outcomes categorized by morphology (M1 vs. M2/M3) and MRD status assessed by flow cytometry (<5% vs. ≥5%). Morphological remission (M1 status) was achieved for 98.6% of B-ALL patients and 93.8% of T-ALL patients at the EOI.[159]
Inferior EFS rates were also observed for patients with T-ALL with M1 marrow and MRD of ≥5% compared with those in concordant remission (87.6% vs. 80.3%). However, outcome for T-ALL patients not in remission (whether by morphology or MRD or both) was superior to that of comparable patients with B-ALL.
A study of 9,350 patients enrolled on COG clinical trials between 2004 and 2014 compared characteristics of patients and their outcomes categorized by morphology (M1 vs. M2/M3) and MRD status assessed by flow cytometry (<5% vs. ≥5%). Morphological remission (M1 status) was achieved for 98.6% of B-ALL patients and 93.8% of T-ALL patients at the EOI.[159]
Factors predictive of discordant MRD (≥5%) for patients in morphological remission at EOI included age 10 years and older, WBC count at presentation of 50,000/µL or higher, neutral or unfavorable cytogenetics, and ETP ALL (for patients with T-ALL).
| Outcome | M1/MRD <5% | P valueb | M1/MRD ≥5% | P valuec | M2/MRD ≥5% | |
|---|---|---|---|---|---|---|
| HR = high risk; MRD = minimal residual disease; SR = standard risk. | ||||||
| aAdapted from Gupta et al.[159] | ||||||
| bP value is comparing M1/MRD <5% with M1/MRD ≥5%. | ||||||
| cP value is comparing M1/MRD ≥5% with M2/MRD ≥5%. | ||||||
| Event-free survival rates: | ||||||
| B-ALL, overall | 87.1% ± 0.4% (n = 7,682) | <.0001 | 59.1% ± 6.5% (n = 66) | .009 | 39.1% ± 7.9% (n = 40) | |
| B-ALL, SR | 90.8% ± 0.4% (n = 5,000) | .25 | 85.9% ± 7.6% (n = 22) | .45 | 76.2% ± 15.2% (n = 9) | |
| B-ALL, HR | 80% ± 0.9% (n = 2,682) | <.0001 | 44.9% ± 8.3% (n = 44) | .05 | 29% ± 8.2% (n = 31) | |
| T-ALL | 87.6% ± 1.5% (n = 1,303) | .01 | 80.3% ± 7.3% (n = 97) | .13 | 62.7% ± 13.5% (n = 40) | |
| Overall survival rates: | ||||||
| B-ALL, overall | 93.8% ± 0.3% (n = 7,682) | <.0001 | 77.2% ± 5.6% (n = 66) | .01 | 59% ± 8.9% (n = 40) | |
| B-ALL, SR | 96.6% ± 0.3% (n = 5,000) | .24 | 95.5% ± 4.6% (n = 22 ) | .75 | 88.9% ± 12.1% (n = 9) | |
| B-ALL, HR | 88.4% ± 0.7% (n = 2,682) | <.0001 | 66.9% ± 8.3% (n = 44) | .06 | 51.4% ± 10.4% (n = 31) | |
| T-ALL | 91.9% ± 1.3% (n = 1,303) | .005 | 83.4% ± 6.8% (n = 97) | .34 | 76.7% ± 12.3% (n = 40) | |
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