Purpose
Severe myelosuppression in patients with acute lymphoblastic leukemia (ALL) undergoing 6-MP-based maintenance therapy is attributed to
TPMT
gene polymorphisms, which is rare in Asian populations. This study aims to evaluate the role of selected polymorphisms in
NUDT15, ITPA
, and
MRP4
genes in addition to
TPMT
in predicting 6-MP intolerance during ALL maintenance therapy.
Patients and Methods
We screened for the presence of
NUDT15*3
(c.415 C>T, rs116855232);
MRP4
c.2269 C>T (rs3765534),
ITPA
c.94 C>A (rs1127354) polymorphisms in addition to
TPMT
*2 (rs1800462), *3A (*3B and *3C; rs1800460 and rs1142345) in ALL patients with documented severe neutropenia (cohort-1; n=42). These polymorphisms were then screened in a prospective cohort of ALL patients (cohort-2; n=133) and compared with 6-MP dose reduction, early/late myelotoxicity.
Results
Nineteen (45%) patients in cohort-1 and 18 (14%) in cohort-2 had
NUDT15
c.415 C>T variant while 4 (3%) patients in cohort-2 had
TPMT*3C
variant. Five (12%) in cohort-1 and 30 (24%) in cohort-2 had
ITPA
c.94 C>A variant while 9 (22%) and 15 (12%) had
MRP4
c.2269 C>T variant in cohorts-1 and 2, respectively. All in cohort-1 and 36 (27%) in cohort-2 had severe myelotoxicity. Twenty-eight patients (66.6%) in cohort-1 and 40 (30%) patients in cohort-2 had significant 6-MP dose reduction.
NUDT15
c.415 C>T variant explained severe myelotoxicity in 63% and 33% in cohort 1 and 2.
TPMT
*3C and
ITPA
c.94 C>A variants also explained myelotoxicity in cohort-2 (Median ANC: 376 vs 1014 mm
3
; p=0.04 and 776 vs 1023 mm
3
; p=0.04 respectively).
NUDT15
c.415 C>T polymorphism explained significant myelotoxicity (507 vs 1298 mm
3
; p<0.0001) in the multivariate analysis as well (β=−0.314, p<0.0001).
Conclusion
NUDT15
c.415 C>T (15*3), TPMT*3C, as well as ITPA c.94 C>A and MRP4 c.2269 C>T polymorphisms explain hematotoxicities. Preemptive genotype-based (
NUDT15*3, TPMT, ITPA
c.94 C>A) 6-MP dosing could improve the outcome after maintenance therapy.