Nina Toft

Methylated metabolites of 6-mercaptopurine are associated with hepatotoxicity

Hepatotoxicity with elevation of aminotransferase levels is common during combined methotrexate and thiopurine therapy. However, the mechanism of hepatotoxicity induced by these drugs remains obscure. We have investigated the relationship of a rise in aminotransferase levels to erythrocyte levels of methotrexate and its polyglutamates, 6‐thioguanine nucleotides, the major cytotoxic metabolites of 6‐mercaptopurine, and methylated metabolites of 6‐mercaptopurine generated by thiopurine methyltransferase in competition with the formation of 6‐thioguanine nucleotides.

Risk group assignment differs for children and adults 1–45 yr with acute lymphoblastic leukemia treated by the NOPHO ALL‐2008 protocol

The prognosis of acute lymphoblastic leukemia is poorer in adults than in children. Studies have indicated that young adults benefit from pediatric treatment, although no upper age limit has been defined.

Complying with the European Clinical Trials directive while surviving the administrative pressure – An alternative approach to toxicity registration in a cancer trial

The European Clinical Trials Directive of 2004 has increased the amount of paper work and reduced the number of initiated clinical trials. Particularly multinational trials have been delayed. To meet this challenge we developed a novel, simplified, fast and easy strategy for on-line toxicity registration for patients treated according to the Nordic/Baltic acute lymphoblastic leukaemia protocol, NOPHO ALL 2008, for children and young adults, including three randomisations. We used a risk-assessment based approach, avoiding reporting of expected adverse events and instead concentrating on 20 well-known serious, but rarer events with focus on changes in therapy introduced in the treatment protocol. This toxicity registration strategy was approved by the relevant regulatory authorities in all seven countries involved, as compliant within the EU directive of 2004. The centre compliance to registration was excellent with 98.9% of all patients being registered within 5weeks from the requested quarterly registration. Currently, four toxicities (thrombosis, fungal infections, pancreatitis and allergic reactions) have been chosen for further detailed exploration due to the cumulative fraction of patients with positive registrations exceeding 5%. This toxicity registration offers real-time toxicity profiles of the total study cohort and provides early warnings of specific toxicities that require further investigation.

Adult acute lymphoblastic leukaemia in Denmark. A national population-based retrospective study on acute lymphoblastic leukaemia in Denmark 1998-2008.

Since July 2008, children and adults 1–45 years, diagnosed with acute lymphoblastic leukaemia (ALL) in Denmark have been treated according to the common Nordic Society for Paediatric Haematology and Oncology ALL2008 protocol. To explore whether this strategy will improve survival compared with historical controls, we performed a retrospective national population‐based study of adult ALL between 1998 and 2008. Patients were identified through the Danish Patobank and the Danish Cancer Registry; data was collected from patient files, and included 277 patients (median age, 47 years, range 15–91 years). The 5‐year projected event‐free survival (pEFS5y) and overall survival (pOS5y) for the whole cohort was 27·5% [95% confidence interval (CI) 22·4–33·6] and 34·1% (95% CI 28·7–40·4), respectively. No patient above 65 years survived beyond 5 years from diagnosis. For patients receiving curatively intended treatment, the pEFS5y and pOS5y were 36·6% and 44·1%, respectively, with a significantly higher pOS5y for patients 15–35 years compared with patients 36–65 years (50·7% vs. 38·9%, P = 0·006). Cox multiple regression analysis identified age (Hazard Ratio = 1·7, P < 0·006) as a statistically significant predictor of EFS. The cure rates, not least for the elderly, are unacceptably low, and call for new strategies in the treatment of adult ALL in all age groups.

Toxicity profile and treatment delays in NOPHO ALL2008-comparing adults and children with Philadelphia chromosome-negative acute lymphoblastic leukemia.

Cure rates improve when adolescents and young adults with acute lymphoblastic leukemia (ALL) are treated according to pediatric protocols. Assumed risks of toxicities and associated delays in treatment have played a role in setting upper age limits. The aim of this study was to examine the toxicity profile and treatment delays in NOPHO ALL2008 comparing children and adults.

Results of NOPHO ALL2008 treatment for patients aged 1–45 years with acute lymphoblastic leukemia

Adults with acute lymphoblastic leukemia (ALL) do worse than children. From 7/2008 to 12/2014, Nordic and Baltic centers treated 1509 consecutive patients aged 1–45 years with Philadelphia chromosome-negative ALL according to the NOPHO ALL2008 without cranial irradiation. Overall, 1022 patients were of age 1–9 years (A), 266 were 10–17 years (B) and 221 were 18–45 years (C). Sixteen patients (three adults) died during induction. All others achieved remission after induction or 1–3 intensive blocks. Subsequently, 45 patients (12 adults) died, 122 patients relapsed (32 adults) with a median time to relapse of 1.6 years and 13 (no adult) developed a second malignancy. Median follow-up time was 4.6 years. Among the three age groups, older patients more often had higher risk ALL due to T-ALL (32%/25%/9%, P<0.001), KMT2A rearrangements (6%/5%/3%, P<0.001) and higher day 29 residual leukemia for B-lineage (P<0.001), but not T-ALL (P=0.53). Event-free survival rates (pEFS5y) were 89±1% (A), 80±3% (B) and 74±4% (C) with significant differences only for non-high risk groups. Except for thrombosis, pancreatitis and osteonecrosis, the risk of 19 specified toxicities was not enhanced by age above 10 years. In conclusion, a pediatric-based protocol is tolerable and effective for young adults, despite their increased frequency of higher risk features.

Genetic analyses of thiopurine methyltransferase polymorphisms in Greenlandic and Danish populations

Aim: To determine the frequency of thiopurine methyltransferase (TPMT) low‐activity alleles in the Greenlandic and Danish populations. Methods: 142 Greenlandic individuals and 200 Danish blood donors were screened for the TPMT G460A and A719G low‐activity alleles. Results: Thiopurine methyltransferase low‐activity alleles were significantly higher in the Greenlandic compared to the Danish population, being 8.1% (95% CI 4.9–11.3) and 3.5% (95% CI 1.7–5.3) (p<0.01), respectively. Except for one Danish patient with an A719G allele (TPMT*3C), all the aberrant alleles were compound G460A and A719G alleles (TPMT*3A).

Thromboembolism in acute lymphoblastic leukemia: results of NOPHO ALL2008 protocol treatment in patients aged 1 to 45 years

Thromboembolism frequently occurs during acute lymphoblastic leukemia (ALL) therapy. We prospectively registered thromboembolic events during the treatment of 1772 consecutive Nordic/Baltic patients with ALL aged 1 to 45 years who were treated according to the Nordic Society of Pediatric Hematology and Oncology ALL2008 protocol (July 2008-April 2017). The 2.5-year cumulative incidence of thromboembolism (N = 137) was 7.9% (95% confidence interval [CI], 6.6-9.1); it was higher in patients aged at least 10 years (P < .0001). Adjusted hazard ratios (HRas) were associated with greater age (range, 10.0-17.9 years: HRa, 4.9 [95% CI, 3.1-7.8; P < .0001]; 18.0-45.9 years: HRa, 6.06 [95% CI, 3.65-10.1; P < .0001]) and mediastinal mass at ALL diagnosis (HRa, 2.1; 95% CI, 1.0-4.3; P = .04). In a multiple absolute risk regression model addressing 3 thromboembolism risk factors, age at least 10 years had the largest absolute risk ratio (RRage, 4.7 [95% CI, 3.1-7.1]; RRenlarged lymph nodes, 2.0 [95% CI, 1.2-3.1]; RRmediastinal mass, 1.6 [95% CI, 1.0-2.6]). Patients aged 18.0 to 45.9 years had an increased hazard of pulmonary embolism (HRa, 11.6; 95% CI, 4.02-33.7; P < .0001), and patients aged 10.0 to 17.9 years had an increased hazard of cerebral sinus venous thrombosis (HRa, 3.3; 95% CI, 1.5-7.3; P = .003) compared with children younger than 10.0 years. Asparaginase was truncated in 38/128 patients with thromboembolism, whereas thromboembolism diagnosis was unassociated with increased hazard of relapse (P = .6). Five deaths were attributable to thromboembolism, and patients younger than 18.0 years with thromboembolism had increased hazard of dying compared with same-aged patients without thromboembolism (both P ≤ .01). In conclusion, patients aged at least 10 years could be candidates for preemptive antithrombotic prophylaxis. However, the predictive value of age 10 years or older, enlarged lymph nodes, and mediastinal mass remain to be validated in another cohort.

Comparing osteonecrosis clinical phenotype, timing, and risk factors in children and young adults treated for acute lymphoblastic leukemia

Treatment‐related osteonecrosis (ON) is a serious complication of treatment of acute lymphoblastic leukemia (ALL).

NT5C2 germline variants alter thiopurine metabolism and are associated with acquired NT5C2 relapse mutations in childhood acute lymphoblastic leukaemia

The antileukaemic drug 6-mercaptopurine is converted into thioguanine nucleotides (TGN) and incorporated into DNA (DNA-TG), the active end metabolite. In a series of genome-wide association studies, we analysed time-weighted means (wm) of erythrocyte concentrations of TGN (Ery-TGN) and DNA-TG in 1009 patients undergoing maintenance therapy for acute lymphoblastic leukaemia (ALL). In discovery analyses (454 patients), the propensity for DNA-TG incorporation (wmDNA-TG/wmEry-TGN ratio) was significantly associated with three intronic SNPs in NT5C2 (top hit: rs72846714; P = 2.09 × 10−10, minor allele frequency 15%). In validation analyses (555 patients), this association remained significant during both early and late maintenance therapy (P = 8.4 × 10−6 and 1.3 × 10−3, respectively). The association was mostly driven by differences in wmEry-TGN, but in regression analyses adjusted for wmEry-TGN (P < 0.0001), rs72846714-A genotype was also associated with a higher wmDNA-TG (P = 0.029). Targeted sequencing of NT5C2 did not identify any missense variants associated with rs72846714 or wmEry-TGN/wmDNA-TG. rs72846714 was not associated with relapse risk, but in a separate cohort of 180 children with relapsed ALL, rs72846714-A genotype was associated with increased occurrence of relapse-specific NT5C2 gain-of-function mutations that reduce cytosol TGN levels (P = 0.03). These observations highlight the impact of both germline and acquired mutations in drug metabolism and disease trajectory.