Chemotherapy and Anticancer Drugs Adjustment in Obesity: A Narrative Review

BACKGROUND

Obese individuals have higher rates of cancer incidence and cancer- related mortality. The worse chemotherapy outcomes observed in this subset of patients are multifactorial, including the altered physiology in obesity and its impact on pharmacokinetics, the possible increased risk of underdosing, and treatment-related toxicity.

AIMS

The present review aimed to discuss recent data on physiology, providing just an overall perspective and pharmacokinetic alterations in obesity concerning chemotherapy. We also reviewed the controversies of dosing adjustment strategies in adult and pediatric patients, mainly addressing the use of actual total body weight and ideal body weight.

METHODS

This narrative review tried to provide the best evidence to support antineoplastic drug dosing strategies in children, adolescents, and adults.

RESULTS

Cardiovascular, hepatic, and renal alterations of obesity can affect the distribution, metabolism, and clearance of drugs. Anticancer drugs have a narrow therapeutic range, and variations in dosing may result in either toxicity or underdosing. Obese patients are underrepresented in clinical trials that focus on determining recommendations for chemotherapy dosing and administration in clinical practice. After considering associated comorbidities, the guidelines recommend that chemotherapy should be dosed according to body surface area (BSA) calculated with actual total body weight, not an estimate or ideal weight, especially when the intention of therapy is the cure.

CONCLUSION

The actual total body weight dosing appears to be a better approach to dosing anticancer drugs in both adults and children when aiming for curative results, showing no difference in toxicity and no limitation in treatment outcomes compared to adjusted doses.

Drug pharmacokinetics in the obese population: challenging common assumptions on predictors of obesity-related parameter changes

INTRODUCTION

Obesity is associated with many physiological changes. We review available evidence regarding five commonly accepted assumptions to a priori predict the impact of obesity on drug pharmacokinetics (PK).

AREAS COVERED

The investigated assumptions are: 1) lean body weight is the preferred descriptor of clearance and dose adjustments; 2) volume of distribution increases for lipophilic, but not for hydrophilic drugs; 3) CYP-3A4 activity is suppressed and UGT activity is increased, implying decreased and increased dose requirements for substrates of these enzyme systems, respectively; 4) glomerular filtration rate is enhanced, necessitating higher doses for drugs cleared through glomerular filtration; 5) drug dosing information from obese adults can be extrapolated to obese adolescents.

EXPERT OPINION

Available literature contradicts, or at least limits the generalizability, of all five assumptions. Clinical studies should focus on quantifying the impact of duration and severity of obesity on drug PK in adults and adolescents, and also include oral bioavailability and pharmacodynamics in these studies. Physiologically-based PK approaches can be used to predict PK changes for individual drugs, but can also be used to define in general terms based on patient characteristics and drug properties, when certain assumptions can or cannot be expected to be systematically accurate.

Opioids for acute pain management in children

Opioids are integral to multimodal analgesic regimens in children with moderate to severe acute pain. Throughout normal childhood there are marked changes in physiology, and social and psychological development that influence the perception and expression of pain, the pharmacology of opioids, and how they are used. A multidimensional pain assessment is key to guiding appropriate opioid prescribing. Most of the commonly used opioids in adults are used in children, with the increasing exception of codeine (as a result of regulatory change), and are generally well tolerated. Patient groups at increased risk of ventilatory impairment include neonates and those with obstructive sleep apnoea, severe neurodevelopmental conditions, trisomy 21, and severe epilepsy. Slow-release opioids are not recommended for general use, but may be used in select populations, for example, following scoliosis surgery, major trauma or burns. Prescribing and administration errors are a major issue in paediatrics generally; the potential consequences of opioid prescribing or administration errors are serious, particularly following hospital discharge. Opioids prescribed at discharge are frequently in excess of a child's analgesic requirements; three to five days supply appears sufficient for the majority of common paediatric operations. Discharge opioid prescriptions have been linked to long-term opioid use in adolescents with risk factors. Misuse of prescription opioids by adolescents is also concerning, with prevalence estimates ranging from 1.1% to 20%. Caregivers have a tendency to underdose opioids in their children; caregiver education may improve appropriate administration. Caregivers must also be provided with instructions on safe storage and disposal of unused opioids.

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.

Extracorporeal life support in adult patients with out-of-hospital cardiac arrest

The use of extracorporeal life support in cardiopulmonary resuscitation (CPR) of adult patients experiencing out-of-hospital cardiac arrest by the application of veno-arterial extracorporeal membrane oxygenation (ECMO) during cardiac arrest has been increasing over the past decade. This can be attributed to the encouraging results of extracorporeal CPR (ECPR) in multiple observational studies. To date, only one randomised controlled trial has compared ECPR to conventional advanced life support measures. Patient selection is crucial for the success of ECPR programmes. A rapid and organised approach is required for resuscitation, i.e. cannula insertion with ECMO pump initiation in combination with other aspects of post-cardiac arrest care such as targeted temperature management and early coronary reperfusion. The provision of an ECPR service can be costly, resource intensive and technically challenging, as limited studies have reported on its cost-effectiveness.

Obesity and anesthetic pharmacology: simulation of target-controlled infusion models of propofol and remifentanil

The prevalence of obesity is increasing, resulting in an increase in the number of surgeries performed to treat obesity and diseases induced by obesity. The associated comorbidities as well as the pharmacokinetic and pharmacodynamic changes that occur in obese patients make it difficult to control the appropriate dose of anesthetic agents. Factors that affect pharmacokinetic changes include the increase in adipose tissue, lean body weight, extracellular fluid, and cardiac output associated with obesity. These physiological and body compositional changes cause changes in the pharmacokinetic and pharmacodynamic parameters. The increased central volume of distribution and alterations in the clearance of drugs affect the plasma concentration of propofol and remifentanil in the obese population. Additionally, obesity can affect pharmacodynamic properties, such as the 50% of maximal effective concentration and the effect-site equilibration rate constant (ke0). Conducting a simulation of target-controlled infusions based on pharmacokinetic and pharmacodynamic models that include patients that are obese can help clinicians better understand the pharmacokinetic and pharmacodynamic changes of anesthetic drugs associated with this population.

Model-Informed Precision Dosing of Antibiotics in Pediatric Patients: A Narrative Review

Optimal pharmacotherapy in pediatric patients with suspected infections requires understanding and integration of relevant data on the antibiotic, bacterial pathogen, and patient characteristics. Because of age-related physiological maturation and non-maturational covariates (e.g., disease state, inflammation, organ failure, co-morbidity, co-medication and extracorporeal systems), antibiotic pharmacokinetics is highly variable in pediatric patients and difficult to predict without using population pharmacokinetics models. The intra- and inter-individual variability can result in under- or overexposure in a significant proportion of patients. Therapeutic drug monitoring typically covers assessment of pharmacokinetics and pharmacodynamics, and concurrent dose adaptation after initial standard dosing and drug concentration analysis. Model-informed precision dosing (MIPD) captures drug, disease, and patient characteristics in modeling approaches and can be used to perform Bayesian forecasting and dose optimization. Incorporating MIPD in the electronic patient record system brings pharmacometrics to the bedside of the patient, with the aim of a consisted and optimal drug exposure. In this narrative review, we evaluated studies assessing optimization of antibiotic pharmacotherapy using MIPD in pediatric populations. Four eligible studies involving amikacin and vancomycin were identified from 418 records. Key articles, independent of year of publication, were also selected to highlight important attributes of MIPD. Although very little research has been conducted until this moment, the available data on vancomycin indicate that MIPD is superior compared to conventional dosing strategies with respect to target attainment. The utility of MIPD in pediatrics needs to be further confirmed in frequently used antibiotic classes, particularly aminoglycosides and beta-lactams.

Neuromuscular Blockade Correlates with Hormones and Body Composition in Acromegaly

Tumor resection is the first-line therapy for acromegaly patients. In some cases, unsatisfactory intraoperative neuromuscular blockades (NMBs) lead to failed operations. The purpose of this study was to investigate and quantify the NMB status of acromegaly patients and explore the relationship between NMB status and hormone levels and body composition. Twenty patients with untreated acromegaly and seventeen patients with nonfunctioning pituitary adenomas as controls were enrolled in this study. NMB was assessed using the train-of-four (TOF) technique with TOF-Watch® SX. The onset time of NMB, deep neuromuscular blockade duration (DNMBD), and clinical neuromuscular blockade duration (CNMBD) were monitored. We found a significantly longer onset time (110.25 ± 54.90 vs. 75.00 ± 27.56, s, p=0.017), shorter DNMBD (21.99 ± 5.67 vs. 34.96 ± 11.04, min, p < 0.001), and shorter CNMBD (33.26 ± 8.09 vs. 46.21 ± 10.89, min, p < 0.001) in acromegaly patients compared with the controls. DNMBD and CNMBD decreased in patients with decreasing body fat percentage and increasing growth hormone (GH) level, insulin-like growth factor 1 (IGF-1) level, and GH and IGF-1 burden. The onset time increased with increasing IGF-1 level and GH and IGF-1 burden. Taken together, a unique NMB status was identified in acromegaly patients with the following characteristics: prolonged onset time and shortened DNMBD and CNMBD. Changes in the levels and burdens of GH and IGF-1 and body composition were linearly correlated with intraoperative NMB in acromegaly patients.

Comparison of Clinical Outcomes and Medication Use of Obese Versus Nonobese Children Admitted to the Pediatric Intensive Care Unit

Background: Few studies have compared clinical outcomes and medication use between obese and nonobese children in the pediatric intensive care unit (PICU). Objectives: The primary objective was to compare clinical outcomes including mortality, PICU length of stay (LOS), and mechanical ventilation (MV) requirement between obese and nonobese children. Secondary objectives included analysis of factors associated with these outcomes and medication use between groups. Methods: This retrospective study included children 2 to 17 years old admitted to the PICU over a 1-year time frame. Patients were categorized as obese, body mass index (BMI) ≥ 95th percentile, and nonobese (BMI < 95th percentile). Three binary regression models assessed the impact of obesity on clinical outcomes. Results: There were 834 admissions, with 22.1% involving obese children. There was no difference in mortality, MV requirement, or PICU LOS between groups. There were no associations with obesity and clinical outcomes found, but an association was noted for medication classes and receipt of continuous infusions on clinical outcomes. There was no difference noted in the median number (interquartile range [IQR]) of medications between obese and nonobese children, 8 (6-13) versus 9 (6-15), P = .38, but there was a difference in patients receiving a continuous infusion between obese and nonobese children, 24.4% versus 8.8%, P < .01. The 15 most used medications in both groups included analgesics, antimicrobials, corticosteroids, bronchodilators, and gastrointestinal agents. Conclusions: One-fifth of all admissions included obese children. Obesity was not associated with mortality, PICU LOS, and MV requirement, but the number of medication classes and continuous infusions were associated with these outcomes.