Treatment-related sinusoidal obstruction syndrome in children with de novo acute lymphoblastic leukemia during intensification

6-Mercaptopurine-associated Sinusoidal Obstructive Syndrome During Interim Maintenance I: A Case Report

Thiopurine-methyltransferase (TPMT) and nudix-hydrolase-15 (NUDT15) are enzymes relevant to the metabolism of thiopurine medications, used to treat immunologic disorders and malignancies. Standard dosing administered in the setting of TPMT/NUDT15 dysfunction can cause excessive cytotoxic metabolites and life-threatening complications. We describe an adolescent with high-risk B-cell acute lymphoblastic leukemia (ALL) whose TPMT/NUDT15 status was unknown due to lack of insurance approval for genetic testing. He subsequently developed myelosuppression and severe veno-occlusive disease (VOD) after receiving 6-mercaptopurine (6-MP). Our patient provides an example of a very rare 6-MP-related toxicity and the potential benefit of TPMT/NUDT15 screening before initiating thiopurine therapy.

Sinusoidal Obstruction Syndrome of the Liver Associated With 6-Mercaptopurine During Maintenance in a Child With T-cell Acute Lymphoblastic Leukemia

Sinusoidal obstruction syndrome (SOS) of the liver is a complication of chemotherapy most often encountered with hematopoietic stem cell transplant due to high-dose conditioning regimens, but it can also occur with regimens outside of the transplant setting. Mild-to-moderate SOS is a well-described 6-thioguanine toxicity; however, it has rarely been reported as secondary to 6-mercaptopurine, a related thiopurine. This report details a case of a 10-year-old male with T-cell acute lymphoblastic leukemia who developed severe SOS during maintenance therapy with 6-mercaptopurine, and a review of the related literature.

Two Cases of Veno-occlusive Disease/Sinusoidal Obstruction Syndrome After Thioguanine Treatment for Acute Lymphoblastic Leukemia

Veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) is a potentially life-threatening complication of hematopoietic cell transplantation conditioning or high-dose chemotherapy. The underlying pathogenesis involves toxic injury to hepatocytes and sinusoidal endothelial cells. Presenting symptoms include ascites, weight gain, hepatomegaly, and hyperbilirubinemia. Severe VOD/SOS with multiorgan failure has a mortality rate of >80% if left untreated. Thioguanine, a chemotherapy drug used to treat acute lymphoblastic leukemia, has been shown to cause VOD/SOS. Here, we describe cases of 2 patients who developed very severe VOD/SOS after starting thioguanine for acute lymphoblastic leukemia; both achieved complete remission with defibrotide and experienced no defibrotide-related adverse events.

Hepatic sinusoidal obstruction syndrome and short-term application of 6-thioguanine in pediatric acute lymphoblastic leukemia

Long-term treatment with 6-thioguanine (6-TG) for pediatric acute lymphoblastic leukemia (ALL) is associated with high rates of hepatic sinusoidal obstruction syndrome (SOS). Nevertheless, current treatment continues to use short-term applications of 6-TG with only sparse information on toxicity. 6-TG is metabolized by thiopurine methyltransferase (TPMT) which underlies clinically relevant genetic polymorphism. We analyzed the association between hepatic SOS reported as a serious adverse event (SAE) and short-term 6-TG application in 3983 pediatric ALL patients treated on trial AIEOP-BFM ALL 2000 (derivation cohort) and defined the role of TPMT genotype in this relationship. We identified 17 patients (0.43%) with hepatic SOS, 13 of which with short-term exposure to 6-TG (P < 0.0001). Eight of the 13 patients were heterozygous for low-activity TPMT variants, resulting in a 22.4-fold (95% confidence interval 7.1-70.7; P ≤ 0.0001) increased risk of hepatic SOS for heterozygotes in comparison to TPMT wild-type patients. Results were supported by independent replication analysis. All patients with hepatic SOS after short-term 6-TG recovered and did not demonstrate residual symptoms. Thus, hepatic SOS is associated with short-term exposure to 6-TG during treatment of pediatric ALL and SOS risk is increased for patients with low-activity TPMT genotypes.

Understanding thiopurine methyltransferase polymorphisms for the targeted treatment of hematologic malignancies

INTRODUCTION

Thiopurine methyltransferase (TPMT) catalyzes the S-methylation of thiopurines (mercaptopurine (MP) and tioguanine (TG)), chemotherapeutic agents used in the treatment of acute lymphoblastic leukemia (ALL). Polymorphisms in TPMT gene encode diminished activity enzyme, enhancing accumulation of active metabolites, and partially explaining the inter-individual differences in patients' clinical response.

AREAS COVERED

This review gives an overview on TPMT gene and function, and discusses the pharmacogenomic implications of TPMT variants in the prevention of severe thiopurine-induced hematological toxicities and the less known implication on TG-induced sinusoidal obstruction syndrome. Additional genetic and non-genetic factors impairing TPMT activity are considered. Literature search was done in PubMed for English articles published since1990, and on PharmGKB.

EXPERT OPINION

To titrate thiopurines safely and effectively, achieve the right degree of lymphotoxic effect and avoid excessive myelosuppression, the optimal management will combine a preemptive TPMT genotyping to establish a safe initial dose with a close phenotypic monitoring of TPMT activity and/or of active metabolites during long-term treatment. Compared to current ALL protocols, replacement of TG by MP during reinduction phase in TPMT heterozygotes and novel individualized TG regimens in maintenance for TPMT wild-type subjects could be investigated to improve outcomes while avoiding risk of severe hepatotoxicity.

Anatomic and Clinical Pathology Characterization of Drug-Induced Sinusoidal Obstruction Syndrome (Veno-Occlusive Disease) in Cynomolgus Macaques

Sinusoidal obstruction syndrome (SOS) is a unique form of liver injury that occurs after exposure to chemotherapeutic drugs and toxins. The diagnosis of SOS in humans remains a challenge as the clinical criteria have low specificity and there are no reliable noninvasive biomarkers. The mechanism of injury is believed to be damage to liver endothelial cells, primarily sinusoidal endothelial cells (SECs), which leads to sinusoidal dilation, central venous fibrosis, and/or nodular regeneration. Nonclinical data suggest that this uncommon liver toxicity can be recapitulated in cynomolgus monkeys, and it is critical that pathologists are familiar with its characteristic clinicopathologic features. Elevations in liver enzymes, in particular aspartate aminotransferase, associated with isolated thrombocytopenia, should raise the suspicion of SEC injury for specific drug classes. Characterization of liver microscopic findings in monkeys benefits from the use of appropriate stains, such as reticulin stain, and VEGFR2 and CD34 immunohistochemical (IHC) stains. CD41 IHC demonstrates platelet accumulation in injured sinusoids, the likely cause of thrombocytopenia commonly reported in SOS. In conclusion, this report provides a comprehensive characterization of the pathology findings of drug-induced SOS in monkeys with the objectives of ensuring appropriate nonclinical recognition of the liability and informing clinical development strategy and monitoring.

Ocular hemorrhage secondary to thioguanine-associated veno-occlusive disease in a child with acute lymphoblastic leukemia in delayed intensification

Hepatic VOD is a potentially fatal complication during stem cell transplantation and is rarely seen in the non-transplant setting. We report the case of a five-year-old boy who presented with visual complaints during delayed intensification phase of treatment for ALL. He was found to have bilateral retinal hemorrhages associated with profound thrombocytopenia due to chemotherapy. VOD was diagnosed based on EBMT criteria and was managed with supportive care. Despite resolution of VOD, his vision progressively deteriorated and resulted in blindness. This case highlights the significance of close monitoring of ALL patients in delayed intensification when they are at risk for developing VOD, the importance of refractory thrombocytopenia as a diagnostic feature and the potential for VOD to manifest with intraocular bleeding.

Sinusoidal obstruction syndrome in a paediatric patient with acute lymphoblastic leukaemia after completion of reinduction therapy according to ALL Intercontinental Berlin-Frankfurt-Münster 2009

Sinusoidal obstruction syndrome (SOS), also termed veno-occlusive disease (VOD) of the liver, is a well-known complication of haematopoietic stem cell transplantation (HSCT) both in children and adults. In the medical literature there are occasional reports of SOS in patients receiving conventional chemotherapy. In children with solid tumours this entity occurs during treatment of nephroblastoma, rhabdomyosarcoma, and medulloblastoma. In the late 1990s SOS was quite often observed as the complication of oral 6-thioguanine (6-TG) in patients suffering from acute lymphoblastic leukaemia (ALL), who received 6-TG throughout maintenance. In current protocols, the syndrome has become uncommon because treatment with 6-TG is limited to two weeks of oral therapy. Here, we report a case of a nine-year-old boy with ALL, who developed sinusoidal obstruction syndrome shortly after completing the reinduction block of chemotherapy (cyclophosphamide, cytarabine, thioguanine) according to the ALL Intercontinental Berlin-Frankfurt-Münster 2009 (ALL IC BFM 2009) treatment protocol.

Defibrotide for the treatment of hepatic veno-occlusive disease/sinusoidal obstruction syndrome following nontransplant-associated chemotherapy: Final results from a post hoc analysis of data from an expanded-access program

BACKGROUND

Hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) is a potentially fatal complication of conditioning for hematopoietic stem cell transplantation (HSCT) but can occur after nontransplant-associated chemotherapy. Following HSCT, VOD/SOS with multi-organ dysfunction (MOD) may be associated with >80% mortality. Defibrotide is approved to treat severe hepatic VOD/SOS post-HSCT in patients aged >1 month in the European Union and hepatic VOD/SOS with renal or pulmonary dysfunction post-HSCT in the United States. Prior to US approval, defibrotide was available to treat VOD/SOS through an expanded-access treatment (T-IND) program. A post hoc analysis of nontransplant-associated VOD/SOS patients treated with defibrotide initiated within 30 days of starting chemotherapy and followed for 70 days is presented.

PROCEDURE

Patients were diagnosed by Baltimore or modified Seattle criteria or biopsy, and received defibrotide 25 mg/kg/day in four divided doses (≥21 days recommended).

RESULTS

Of the 1,154 patients in the T-IND, 137 had nontransplant-associated VOD/SOS, 82 of whom developed VOD/SOS within 30 days of starting chemotherapy. Of them, 66 (80.5%) were aged ≤16 years. Across all the 82 patients, Kaplan-Meier estimated day +70 survival was 74.1%, 65.8% in patients with MOD (n = 38), and 81.3% in patients without MOD (n = 44). By age group, Kaplan-Meier estimated day +70 survival was 80.1% in pediatric patients (n = 66) and 50.0% in adults (n = 16). Treatment-related adverse events occurred in 26.8%.

CONCLUSIONS

In this post hoc analysis of 82 patients initiating defibrotide within 30 days of starting chemotherapy, Kaplan-Meier estimated survival was 74.1% at 70 days after defibrotide initiation. Safety profile was consistent with prior defibrotide studies.