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6MP adherence in a multiracial cohort of children with acute lymphoblastic leukemia: a Children's Oncology Group study.

ABSTRACT: Durable remissions in children with acute lymphoblastic leukemia (ALL) require a 2-year maintenance phase that includes daily oral 6-mercaptopurine (6MP). Adherence to oral 6MP among Asian-American and African-American children with ALL is unknown. We enrolled 298 children with ALL (71 Asian Americans, 68 African Americans, and 159 non-Hispanic whites) receiving oral 6MP for the maintenance phase. Adherence was measured electronically for 39 803 person-days. Adherence declined from 95.0% (month 1) to 91.8% (month 5, P < .0001). Adherence rates were significantly (P < .0001) lower in Asian Americans (90.0% ± 4.9%) and African Americans (87.1% ± 4.4%), as compared with non-Hispanic whites (95.2% ± 1.3%). Race-specific sociodemographic characteristics helped explain poor adherence (African Americans: low maternal education [less than a college degree: 78.9%, vs at least college degree: 94.6%; P < .0001]; Asian Americans: low-income households [<$50 000: 84.5%, vs ≥$50 000: 96.7%; P = .04]; households without mothers as full-time caregivers [85.6%] vs households with mothers as full-time caregivers [97.2%; P = .05]). Adherence rate below 90% was associated with increased relapse risk (hazard ratio, 3.9; P = .01). Using an adherence rate <90% to define nonadherence, 20.5% of the participants were nonadherers. We identify race-specific determinants of adherence, and define a clinically relevant level of adherence needed to minimize relapse risk in a multiracial cohort of children with ALL. This trial was registered at www.clinicaltrials.gov as #NCT00268528.

SUBMITTER: Bhatia S

PROVIDER: S-EPMC4192748 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:PurposeChildren's Oncology Group (COG) AALL0331 tested whether intensified postinduction therapy that improves survival in children with high-risk B-cell acute lymphoblastic leukemia (ALL) would also improve outcomes for those with standard-risk (SR) ALL.Patients and methodsAALL0331 enrolled 5,377 patients between 2005 and 2010. All patients received a 3-drug induction with dexamethasone, vincristine, and pegaspargase (PEG) and were then classified as SR low, SR average, or SR high. Patients with SR-average disease were randomly assigned to receive either standard 4-week consolidation (SC) or 8-week intensified augmented Berlin-Frankfurt-Münster (BFM) consolidation (IC). Those with SR-high disease were nonrandomly assigned to the full COG-augmented BFM regimen, including 2 interim maintenance and delayed intensification phases.ResultsThe 6-year event-free survival (EFS) rate for all patients enrolled in AALL0331 was 88.96% ± 0.46%, and overall survival (OS) was 95.54% ± 0.31%. For patients with SR-average disease, the 6-year continuous complete remission (CCR) and OS rates for SC versus IC were 87.8% ± 1.3% versus 89.1% ± 1.2% (P = .52) and 95.8% ± 0.8% versus 95.2% ± 0.8% (P = 1.0), respectively. Those with SR-average disease with end-induction minimal residual disease (MRD) of 0.01% to < 0.1% had an inferior outcome compared with those with lower MRD and no improvement with IC (6-year CCR: SC, 77.5% ± 4.8%; IC, 77.1% ± 4.8%; P = .71). At 6 years, the CCR and OS rates among 635 nonrandomly treated patients with SR-high disease were 85.55% ± 1.49% and 92.97% ± 1.08%, respectively.ConclusionThe 6-year OS rate for > 5,000 children with SR ALL enrolled in AALL0331 exceeded 95%. The addition of IC to treatment for patients with SR-average disease did not improve CCR or OS, even in patients with higher MRD, in whom it might have been predicted to provide more value. The EFS and OS rates are excellent for this group of patients with SR ALL, with particularly good outcomes for those with SR-high disease.

Project description:ImportanceVariability in prescribed doses of 6-mercaptopurine (6MP) and lack of adherence to a 6MP treatment regimen could result in intra-individual variability in systemic exposure to 6MP (measured as erythrocyte thioguanine nucleotide [TGN] levels) in children with acute lymphoblastic leukemia (ALL). The effect on relapse risk of this variability is unknown.ObjectiveTo determine the effect of high intra-individual variability of 6MP systemic exposure on relapse risk in children with ALL.Design, setting, and participantsWe used a prospective longitudinal design (Children's Oncology Group study [COG-AALL03N1]) to monitor 6MP and disease relapse in 742 children with ALL in ambulatory care settings of 94 participating institutions from May 30, 2005, to September 9, 2011. All participants met the following eligibility criteria: (1) diagnosis of ALL at 21 years or younger; (2) first continuous remission in progress at the time of study entry; (3) receiving self-, parent-, or caregiver-administered oral 6MP during maintenance therapy; and (4) completion of at least 6 months of maintenance therapy at the time of study enrollment. The median patient age at diagnosis was 5 years; 68% were boys; and 43% had National Cancer Institute-based high-risk disease.Main outcomes and measuresDaily 6MP regimen adherence was measured over 68 716 person-days using an electronic system that recorded the date and time of each 6MP bottle opening; adherence rate was defined as the ratio of days that a 6MP bottle was opened to days thata 6MP bottle was prescribed. Average monthly 6MP dose intensity was measured over 120 439 person-days by dividing the number of 6MP doses actually prescribed by the number of planned protocol doses (75 mg/m2/d). Monthly erythrocyte TGN levels (pmol/8 × 108 erythrocytes) were measured over 6 consecutive months per patient (n = 3944 measurements). Using intra-individual coefficients of variation (CV%), patients were classified as having stable (CV% <85th percentile) vs varying (CV% ≥85th percentile) indices. Median follow-up time was 6.7 years from the time of diagnosis.ResultsAdjusting for clinical prognosticators, we found that patients with 6MP nonadherence (mean adherence rate <95%) were at a 2.7-fold increased risk of relapse (95% CI, 1.3-5.6; P = .01) compared with patients with a mean adherence rate of 95% or greater. Among adherers, high intra-individual variability in TGN levels contributed to increased relapse risk (hazard ratio, 4.4; 95% CI, 1.2-15.7; P = .02). Furthermore, adherers with varying TGN levels had varying 6MP dose intensity (odds ratio [OR], 4.5; 95% CI, 1.5-13.4; P = .01) and 6MP drug interruptions (OR, 10.2; 95% CI, 2.2-48.3; P = .003).Conclusions and relevanceThese findings emphasize the need to maximize 6MP regimen adherence and maintain steady thiopurine exposure to minimize relapse in children with ALL.

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6MP adherence in a multiracial cohort of children with acute lymphoblastic leukemia: a Children's Oncology Group study.

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