Perspectives and Expertise in Establishing a Therapeutic Drug Monitoring Programme for Challenging Childhood Cancer Patient Populations

The utility of Therapeutic Drug Monitoring (TDM) in the setting of childhood cancer is a largely underused tool, despite the common use of cytotoxic chemotherapeutics. While it is encouraging that modern advances in chemotherapy have transformed outcomes for children diagnosed with cancer, this has come at the cost of an elevated risk of life-changing long-term morbidity and late effects. This concern can limit the intensity at which these drugs are used. Widely used chemotherapeutics exhibit marked inter-patient variability in drug exposures following standard dosing, with fine margins between exposures resulting in toxicity and those resulting in potentially suboptimal efficacy, thereby fulfilling criteria widely accepted as fundamental for TDM approaches. Over the past decade in the UK, the paediatric oncology community has increasingly embraced the potential benefits of utilising TDM for particularly challenging patient groups, including infants, anephric patients and those receiving high dose chemotherapy. This has been driven by a desire from paediatric oncologists to have access to clinical pharmacology information to support dosing decisions being made. This provides the potential to modify doses between treatment cycles based on a comprehensive set of clinical information, with individual patient drug exposures being used alongside clinical response and tolerability data to inform dosing for subsequent cycles. The current article provides an overview of recent experiences of conducting TDM in a childhood cancer setting, from the perspectives of the clinicians, scientists and pharmacists implementing TDM-based dosing recommendations. The ongoing programme of work has facilitated investigations into the validity of current approaches to dosing for some of the most challenging childhood cancer patient groups, with TDM approaches now being expanded from well-established cytotoxic drugs through to newer targeted treatments.

ML-18 High-dose chemotherapy supported by autologous stem cell transplant in relapsed and refractory primary CNS lymphoma

While whole brain radiation therapy (WBRT) has been performed as consolidation therapy in primary central nervous system lymphoma (PCNSL), high-dose chemotherapy supported by autologous stem cell transplant (HDC/ASCT) is widely investigated today as an alternative treatment strategy, given the high risk for radiation-induced neurotoxicity in WBRT. Various conditioning regimens have been investigated in phase II trials, which report non-inferiority of HDC/ASCT in efficacy and preservation of neurocognitive function in comparison with WBRT. Besides its promising efficacy, treatment-related deaths are reported in 11% in patients treated by a conditioning regimen using thiotepa, busulfan and cyclophosphamide (TBC), which raises a concern for safety. Among several conditioning regimens, analysis using registry data of Japan Society for Hematopoietic Cell Transplantation has revealed that the use of conditioning regimens containing thiotepa was a positive factor for longer PFS. According to the result of a phase I trial in Japan which investigated HDC/ASCT using thiotepa and busulfan (BuTT), thiotepa was approved by the pharmaceuticals and medical devices agency (PMDA) on March 2020. In comparison with the TBC regimen, cyclophosphamide is omitted, and the dose of thiotepa is lower (250 mg/m2, 3 days in TBC; 5 mg/kg, 2 days in BuTT) in BuTT, therefore BuTT could be less toxic in comparison with TBC, and no treatment-related deaths were observed in the phase I study in Japan. Further investigation on the efficacy and safety of BuTT in actual clinical practice is warranted. We have constituted a multi-disciplinary team in our institution in order to perform HDC/ASCT using BuTT in relapsed/refractory PCNSL. Treatment indications are as follows; 65 years old or younger, previously treated by rituximab, methotrexate, procarbazine and vincristine (R-MPV), good organ function and neurological status. Future directions along with preliminary treatment results will be discussed at the meeting.

Mechanisms, Characteristics, and Treatment of Neuropathic Pain and Peripheral Neuropathy Associated with Dinutuximab in Neuroblastoma Patients

Prognosis of metastatic neuroblastoma is very poor. Its treatment includes induction chemotherapy, surgery, high-dose chemotherapy, radiotherapy, and maintenance with retinoic acid, associated with the anti-GD2 monoclonal antibody (ch14.18) dinutuximab. Immunotherapy determined a significant improvement in survival rate and is also utilized in relapsed and resistant neuroblastoma patients. Five courses of dinutuximab 100 mg/m2 are usually administered as a 10-day continuous infusion or over 5 consecutive days every 5 weeks. Dinutuximab targets the disialoganglioside GD2, which is highly expressed on neuroblastoma cells and minimally present on the surface of normal human neurons, peripheral pain fibers, and skin melanocytes. Anti GD2 antibodies bind to surface GD2 and determine the lysis of neuroblastoma cells induced by immune response via the antibody-dependent cellular cytotoxicity and the complement-dependent cytotoxicity. Dinutuximab has significant side effects, including neuropathic pain, peripheral neuropathy, hypersensitivity reactions, capillary leak syndrome, photophobia, and hypotension. The most important side effect is neuropathic pain, which is triggered by the same antibody–antigen immune response, but generates ectopic activity in axons, which results in hyperalgesia and spontaneous pain. Pain can be severe especially in the first courses of dinutuximab infusion, and requires the administration of gabapentin and continuous morphine infusion. This paper will focus on the incidence, mechanisms, characteristics, and treatment of neuropathic pain and peripheral neuropathy due to dinutuximab administration in neuroblastoma patients.