Material and Method:
Our study included pediatric ALL patients treated with the modified St
Jude Total Therapy XV (Total XV) protocol during January 2011- December
2018, aged 1-18 years, who were diagnosed, and completed all the
treatment in our hospital and followed up without interrupting their
follow-up. Patients who were younger than 12 months of age at the time
of admission, biphenotypic feature, had previous diagnoses such as
myelodysplastic syndrome and Fanconi aplastic anemia, had previously
received chemotherapy for other reasons, relapsed ALL patients, patients
who did not come for regular follow-ups, continued their treatment in
other centers and the patients who came to our hospital from other
centers were excluded from the study. Again, the study did not include
patients with mature B-cell (Burkitt) leukemia with different treatment
protocols.
For the diagnosis of ALL, bone marrow aspiration was performed to
evaluate the morphological findings in the staining of slides with
Giemsa. Also, a 10 mL sample was taken from the bone marrow into an
ethylenediaminetetraacetic acid (EDTA) tube, and cell surface markers of
the blastic population were studied with flow cytometry (BD FACSCanto,
BD Biosciences USA). Blastic cell populations for over 25% with flow
cytometry were also diagnosed as ALL.
To classify risk groups, FISH and PCR methods were used to analyses and
evaluate t(9;22) (q34;q11.2); BCR_ABL, t(12;21) (p13;q22); TEL-AML1
(ETV6-RUNX1), t(1;19) (q23;p13.3); TCF3-PBX1, t(v;11q23) (MLL
rearranged) regions and chromosome analysis was performed via
karyotyping. Patients were classified initially into three risk groups
according to St Jude’s Total XV protocol risk criteria based on patient
age and leucocyte count at baseline and leukemic cell phenotype and
genotype. The risk status of the patients was changed according to the
level of minimal residual disease during and after remission induction
therapy. Patients with 1% or higher minimal residual disease on day 19
of remission induction or between 0.01% and 0.99% on day 46 were
included in the standard-risk ALL group. Patients with minimal residual
disease of 1% or higher following completion of remission induction or
0.1% or higher on week 7 of maintenance treatment were included in the
high-risk ALL group.
The patients were treated with the St Jude Children’s Research Hospital
Total XV protocol [15] with a minor modification. (The only
modification was methylprednisolone 20 mg/kg/day for 7 days, 10
mg/kg/day for the second 7 days, and 2 mg/kg/d for other days instead of
prednisolone 40 mg/m2/day orally in the induction phase).[16]
The chemotherapy regimens of all risk groups are summarized in a
supplementary file.
CNS prophylaxis consisted of triple intrathecal therapy (MTX,
cytarabine, and prednisolone), irrespective of the CNS status and the
risk group; the total doses administered were based on the CNS status
and the risk classification and ranged from 13 to 25. The number of
intrathecal therapy doses administered was 13 for LR cases and ranged
from 16 to 25 for IR/HR cases. None of our patients had refractory CNS
leukemia and did not require cranial irradiation.
During treatment, all patients were given trimethoprim-sulfamethoxazole
for Pneumocystis jirovechii prophylaxis, while patients with invasive
fungal infections were given voriconazole prophylaxis until the end of
their treatment. International febrile neutropenia protocols were used
during febrile neutropenia periods, and all patients during febrile
neutropenia periods were hospitalized and given broad-spectrum
antibiotics and, if necessary, antifungal and antiviral
treatments.[17, 18]
If there is an eligible donor, stem cell transplantation was performed
on patients in the HR group or those with MRD positivity at week 7 on
continuation treatment.
Minimal residual disease levels were measured in bone marrow specimens
by multiparameter flow cytometry on days 19 and 46 of remission
induction and weeks 7, 17, 48, and 120 (end of treatment for girls) or
146 (end of treatment for boys) of maintenance treatment. The leukemia
markers that were used to study minimal residual disease by
multiparameter flow cytometry are listed in Table 2.
Data of patients were retrospectively collected using the medical
records in the electronic file system (MEDIN HBYS, Erguvan Information
Technologies, Turkey) for five years, and age, gender, risk group, cell
type, course of the disease, and follow-up period were recorded
electronically (Microsoft Office 2013 package program Excel, Microsoft
USA). Statistical analysis was done with SPSS 20.0 package program (IBM
USA).
After finishing their treatment plan, patients continued to follow-up
evaluations in the pediatric hematology outpatient policlinic every
month during the first 6 months, every other month for the second 6
months, every three months for the next two years, every 6 months for
five years, and then annually thereafter.
As appropriate, comparisons between categorical variables were carried
out using either the Pearson-X² test or Fisher exact test. The duration
of event-free survival (EFS) was calculated from the first day of
treatment to the time of analysis (September 2021) or to the first event
(early death, relapse, or death during remission). EFS and overall
survival (OS) rates were estimated using the Kaplan-Meier method, and
the survival curve was arranged in the SPSS 20.0 for Windows (SPSS Inc.,
Chicago, IL). The Mantel-Cox (Log Rank) test was used to analyze the
factors affecting mortality. A P-value <0.05 was considered
statistically significant.
The study was approved by the institutional ethics committee, and
written informed consent was obtained from parents or guardians at the
beginning of treatment.