A cautionary tale: an evaluation of the performance of treatment switching adjustment methods in a real world case study

BACKGROUND

Treatment switching in randomised controlled trials (RCTs) is a problem for health technology assessment when substantial proportions of patients switch onto effective treatments that would not be available in standard clinical practice. Often statistical methods are used to adjust for switching: these can be applied in different ways, and performance has been assessed in simulation studies, but not in real-world case studies. We assessed the performance of adjustment methods described in National Institute for Health and Care Excellence Decision Support Unit Technical Support Document 16, applying them to an RCT comparing panitumumab to best supportive care (BSC) in colorectal cancer, in which 76% of patients randomised to BSC switched onto panitumumab. The RCT resulted in intention-to-treat hazard ratios (HR) for overall survival (OS) of 1.00 (95% confidence interval [CI] 0.82-1.22) for all patients, and 0.99 (95% CI 0.75-1.29) for patients with wild-type KRAS (Kirsten rat sarcoma virus).

METHODS

We tested several applications of inverse probability of censoring weights (IPCW), rank preserving structural failure time models (RPSFTM) and simple and complex two-stage estimation (TSE) to estimate treatment effects that would have been observed if BSC patients had not switched onto panitumumab. To assess the performance of these analyses we ascertained the true effectiveness of panitumumab based on: (i) subsequent RCTs of panitumumab that disallowed treatment switching; (ii) studies of cetuximab that disallowed treatment switching, (iii) analyses demonstrating that only patients with wild-type KRAS benefit from panitumumab. These sources suggest the true OS HR for panitumumab is 0.76-0.77 (95% CI 0.60-0.98) for all patients, and 0.55-0.73 (95% CI 0.41-0.93) for patients with wild-type KRAS.

RESULTS

Some applications of IPCW and TSE provided treatment effect estimates that closely matched the point-estimates and CIs of the expected truths. However, other applications produced estimates towards the boundaries of the expected truths, with some TSE applications producing estimates that lay outside the expected true confidence intervals. The RPSFTM performed relatively poorly, with all applications providing treatment effect estimates close to 1, often with extremely wide confidence intervals.

CONCLUSIONS

Adjustment analyses may provide unreliable results. How each method is applied must be scrutinised to assess reliability.

Novel risk stratification algorithm for estimating the risk of death in patients with relapsed multiple myeloma: external validation in a retrospective chart review

OBJECTIVES AND DESIGN

A novel risk stratification algorithm estimating risk of death in patients with relapsed multiple myeloma starting second-line treatment was recently developed using multivariable Cox regression of data from a Czech registry. It uses 16 parameters routinely collected in medical practice to stratify patients into four distinct risk groups in terms of survival expectation. To provide insight into generalisability of the risk stratification algorithm, the study aimed to validate the risk stratification algorithm using real-world data from specifically designed retrospective chart audits from three European countries.

PARTICIPANTS AND SETTING

Physicians collected data from 998 patients (France, 386; Germany, 344; UK, 268) and applied the risk stratification algorithm.

METHODS

The performance of the Cox regression model for predicting risk of death was assessed by Nagelkerke's R2, goodness of fit and the C-index. The risk stratification algorithm's ability to discriminate overall survival across four risk groups was evaluated using Kaplan-Meier curves and HRs.

RESULTS

Consistent with the Czech registry, the stratification performance of the risk stratification algorithm demonstrated clear differentiation in risk of death between the four groups. As risk groups increased, risk of death doubled. The C-index was 0.715 (95% CI 0.690 to 0.734).

CONCLUSIONS

Validation of the novel risk stratification algorithm in an independent 'real-world' dataset demonstrated that it stratifies patients in four subgroups according to survival expectation.

Methodology and results of real-world cost-effectiveness of carfilzomib in combination with lenalidomide and dexamethasone in relapsed multiple myeloma using registry data

OBJECTIVE

To predict the real-world (RW) cost-effectiveness of carfilzomib in combination with lenalidomide and dexamethasone (KRd) versus lenalidomide and dexamethasone (Rd) in relapsed multiple myeloma (MM) patients after one to three prior therapies.

METHODS

A partitioned survival model that included three health states (progression-free, progressed disease and death) was built. Progression-free survival (PFS), overall survival (OS) and time to discontinuation (TTD) data for the Rd arm were derived using the Registry of Monoclonal Gammopathies in the Czech Republic; the relative treatment effects of KRd versus Rd were estimated from the phase 3, randomised, ASPIRE trial, and were used to predict PFS, OS and TTD for KRd. The model was developed from the payer perspective and included drug costs, administration costs, monitoring costs, palliative care costs and adverse-event related costs collected from Czech sources.

RESULTS

The base case incremental cost effectiveness ratio for KRd compared with Rd was €73,156 per quality-adjusted life year (QALY) gained. Patients on KRd incurred costs of €117,534 over their lifetime compared with €53,165 for patients on Rd. The QALYs gained were 2.63 and 1.75 for patients on KRd and Rd, respectively.

CONCLUSIONS

Combining the strengths of randomised controlled trials and observational databases in cost-effectiveness models can generate policy-relevant results to allow well-informed decision-making. The current model showed that KRd is likely to be cost-effective versus Rd in the RW and, therefore, the reimbursement of KRd represents an efficient allocation of resources within the healthcare system.

Carfilzomib and dexamethasone versus eight cycles of bortezomib and dexamethasone in patients with relapsed or refractory multiple myeloma: an indirect comparison using data from the phase 3 ENDEAVOR and CASTOR trials

In ENDEAVOR, carfilzomib and dexamethasone (Kd56) demonstrated significant improvement in progression-free survival (PFS) compared with bortezomib and dexamethasone (Vd). Both agents were administered until disease progression; the EU label for Vd, however, stipulates a maximum of eight treatment cycles. Here, matching-adjusted treatment comparison was used to compare efficacy of Kd56 with Vd, if Vd was administered for 8 cycles (Vd-8). Data from ENDEAVOR and CASTOR trials (which compared daratumumab, bortezomib, and dexamethasone with Vd-8) were used. Hazard ratios of PFS were estimated for Vd vs. Vd-8 and Kd vs. Vd-8. For cycles 1-8, risk reduction in PFS for Kd56 vs. Vd-8 was equal to that estimated in ENDEAVOR (HR: 0.53; 95% CI 0.44-0.65). Beyond eight cycles, risk reduction in PFS for Kd56 and Vd-8 was estimated to be 60% (HR: 0.40; 95% CI 0.26-0.63). The analysis suggested that PFS benefit of Kd56 over Vd increases when Vd is given for eight cycles only.

Cost Effectiveness of Blinatumomab Versus Inotuzumab Ozogamicin in Adult Patients with Relapsed or Refractory B-Cell Precursor Acute Lymphoblastic Leukemia in the United States

BACKGROUND AND OBJECTIVE

The TOWER and INO-VATE-ALL trials demonstrated the efficacy and safety of blinatumomab and inotuzumab ozogamicin (inotuzumab), respectively, versus standard-of-care (SOC) chemotherapy in adults with relapsed or refractory (R/R) B-cell precursor acute lymphoblastic leukemia (ALL). The cost effectiveness of blinatumomab versus inotuzumab has not previously been examined.

METHODS

Cost effectiveness of blinatumomab versus inotuzumab in R/R B-cell precursor ALL patients with one or no prior salvage therapy from a United States (US) payer perspective was estimated using a partitioned survival model. Health outcomes were estimated based on published aggregate data from INO-VATE-ALL and individual patient data from TOWER weighted to match patients in INO-VATE-ALL using matching adjusted indirect comparison (MAIC). Analyses were conducted using five approaches relating to use of anchored versus unanchored comparisons of health outcomes and, for the anchored comparisons, the reference treatment to which treatment effects on health outcomes were applied. Estimates from TOWER including the probabilities of complete remission and allogeneic stem-cell transplant (allo-SCT), overall and event-free survival, utilities, duration of therapy, and use of subsequent therapies were MAIC adjusted to match INO-VATE-ALL. Costs of treatment, adverse events, allo-SCT, subsequent therapies, and terminal care were from published sources. A 50-year time horizon and 3% annual discount rate were used.

RESULTS

Incremental costs for blinatumomab versus inotuzumab ranged from US$7023 to US$36,244, depending on the approach used for estimating relative effectiveness. Incremental quality-adjusted life-years (QALYs) ranged from 0.54 to 1.78. Cost effectiveness for blinatumomab versus inotuzumab ranged from US$4006 to US$20,737 per QALY gained.

CONCLUSIONS

Blinatumomab is estimated to be cost effective versus inotuzumab in R/R B-cell precursor ALL adults who have received one or no prior salvage therapy from a US payer perspective.

A cost-effectiveness analysis of denosumab for the prevention of skeletal-related events in patients with multiple myeloma in four European countries: Austria, Belgium, Greece, and Italy

Aim: The approved indication for denosumab (120 mg) was expanded in 2018 to include skeletal-related event (SRE) prevention in patients with multiple myeloma (MM). Therefore, a cost-effectiveness analysis was conducted comparing denosumab with zoledronic acid (ZA) for SRE prevention in patients with MM from the national healthcare system perspective in a representative sample of European countries: Austria, Belgium, Greece, and Italy. Methods: The XGEVA global economic model for patients with MM was used to calculate incremental cost-effectiveness ratios (ICERs) for denosumab vs ZA over a lifetime horizon. Clinical inputs were derived from the denosumab vs ZA randomized, phase 3 study ("20090482") in patients newly-diagnosed with MM, and comprised real-world adjusted SRE rates, serious adverse event (SAE) rates, treatment duration, dose intensity, progression-free survival (PFS), and overall survival (OS). Economic inputs comprised country-specific denosumab and ZA acquisition and administration costs, SRE and SAE management costs, and discount rates. Health utility decrements associated with MM disease progression, SRE and SAE occurrence, and route of administration were included. Results: Estimated ICERs (cost per quality-adjusted life-year [QALY] gained) for denosumab vs ZA in Austria, Belgium, Greece, and Italy were €26,294, €17,737, €6,982, and €27,228, respectively. Using 1-3 times gross domestic product (GDP) per capita per QALY as willingness to pay thresholds, denosumab was 69-94%, 84-96%, 79-96%, and 50-92% likely to be cost-effective vs ZA, respectively. Limitations: Economic inputs were derived from various sources, and time to event inputs were extrapolated from 20090482 study data. Conclusions: Denosumab is cost-effective vs ZA for SRE prevention in patients with MM in Austria, Belgium, Greece, and Italy, based on often-adopted World Health Organization thresholds. This conclusion is robust to changes in model parameters and assumptions. Cost-effectiveness estimates varied across the four countries, reflecting differences in healthcare costs and national economic evaluation guidelines.

Cost-effectiveness of once weekly carfilzomib 70 mg/m2 plus dexamethasone in patients with relapsed and refractory multiple myeloma in the United States

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Background: Carfilzomib plus dexamethasone (Kd) dosed once weekly at 70 mg/m2 (QW Kd70) was recently approved in the US for treating patients with relapsed and refractory multiple myeloma (RRMM). To assess the cost-effectiveness (CE) of QW Kd70 vs twice weekly Kd dosed at 27 mg/m2 (BIW Kd27), data from the phase 3 ARROW trial, which directly compared these regimens in patients with 2-3 prior lines of therapy were used. Methods: A partitioned survival model was developed for the CE analysis. Time to treatment discontinuation, progression-free survival, and overall survival (OS) were estimated from the ARROW trial. Long-term OS was extrapolated using Surveillance Epidemiology and End Results registry data after matching characteristics of patients in the registry and ARROW trial. Direct costs were estimated from a US health care payer perspective. Utilities collected in the ARROW trial using the five-level version of the EuroQol questionnaire (EQ-5D-5L) were applied to estimate the quality-adjusted life years (QALYs). Uncertainty was explored using sensitivity analyses. Two subgroups of patients refractory to lenalidomide or bortezomib were assessed. Main outcomes were mean life-years (LYs), QALYs, lifetime costs, and incremental cost-effectiveness ratios (ICERs). Results: For QW Kd70 and BIW Kd27, the model predicted mean LYs of 4.17 and 3.07 years, QALYs of 2.98 and 2.03 years, and mean total lifetime costs of $444,563 and $373,364, respectively. The incremental LYs gain, QALY gain, and incremental costs of QW Kd70 vs BIW Kd27 were estimated to be 1.10 years, 0.95 year, and $71,199, respectively, resulting in an ICER of $64,595 per LY gained and $75,204 per QALY gained. For patients refractory to lenalidomide and bortezomib, similar results were found with ICERs of $79,988 and $76,793, respectively. Conclusions: In line with ARROW trial results, this CE analysis showed that QW Kd70 is expected to provide considerable additional benefit in terms of LYs and QALYs gained compared with BIW Kd27. In the RRMM setting, QW Kd70 is cost-effective with ICERs below accepted willingness to pay thresholds in US and represents an efficient utilization of the health care budget.

Cost effectiveness (CE) of blinatumomab (BLIN) versus inotuzumab ozogamicin (INO) in adult patients with relapsed/refractory (R/R) acute lymphoblastic leukemia (ALL) with no more than one prior salvage therapy (S0/S1) from a United Kingdom health care perspective

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Background: To estimate Incremental CE Ratio (ICER) of BLIN vs INO in adults with R/R S0/S1 ALL based on matching-adjusted indirect comparison (MAIC) of TOWER and INO-VATE trials from a UK healthcare perspective. Methods: CE was estimated by a partitioned-survival model with outcomes based on published aggregate data from INO-VATE (cutoff: 01/05/2017) and individual patient data from TOWER weighted to match patients in INO-VATE using MAIC. Five analyses were conducted based on alternative approach for the MAIC (anchored through Standard of Care [SOC] vs unanchored), proportional hazard (PH) assumptions, and reference overall survival (OS) distributions. Rates of complete remission and HSCT, utilities, duration of therapy, and use of subsequent therapies also were MAIC adjusted. Due to inconsistent definitions of event-free survival (EFS) between the trials, EFS was assumed to be equal for BLIN and INO complete responders. Costs were estimated from published sources and included those of medicine and administration, key adverse events, HSCT, salvage therapy, and terminal care. Utilities were based on EORTC-8D values derived from EORTC QLQ-C30 assessments in TOWER. A 50-year time horizon was used. Results: In all analyses, BLIN was more costly and more effective than INO. The ICER for BLIN vs INO ranged from £4,014 to £13,371 per QALY. Conclusions: For various approaches for conducting MAIC of BLIN vs INO, BLIN was highly cost effective vs INO in R/R ALL adults with S0/S1 from a UK healthcare perspective. [Table: see text]

Modeling Covariate-Adjusted Survival for Economic Evaluations in Oncology

BACKGROUND AND OBJECTIVES

In economic evaluations in oncology, adjusted survival should be generated if imbalances in prognostic/predictive factors across treatment arms are present. To date, no formal guidance has been developed regarding how such adjustments should be made. We compared various covariate-adjusted survival modeling approaches, as applied to the ENDEAVOR trial in multiple myeloma that assessed carfilzomib plus dexamethasone (Cd) versus bortezomib plus dexamethasone (Vd).

METHODS

Overall survival (OS) data and baseline characteristics were used for a subgroup (bortezomib-naïve/one prior therapy). Four adjusted survival modeling approaches were compared: propensity score weighting followed by fitting a Weibull model to the two arms of the balanced data (weighted data approach); fitting a multiple Weibull regression model including prognostic/predictive covariates to the two arms to predict survival using the mean value of each covariate and using the average of patient-specific survival predictions; and applying an adjusted hazard ratio (HR) derived from a Cox proportional hazard model to the baseline risk estimated for Vd.

RESULTS

The mean OS estimated by the weighted data approach was 6.85 years (95% confidence interval [CI] 4.62-10.70) for Cd, 4.68 years (95% CI 3.46-6.74) for Vd, and 2.17 years (95% CI 0.18-5.06) for the difference. Although other approaches estimated similar differences, using the mean value of covariates appeared to yield skewed survival estimates (mean OS was 7.65 years for Cd and 5.40 years for Vd), using the average of individual predictions had limited external validity (implausible long-term OS predictions with > 10% of the Vd population alive after 30 years), and using the adjusted HR approach overestimated uncertainty (difference in mean OS was 2.03, 95% CI - 0.17 to 6.19).

CONCLUSIONS

Adjusted survival modeling based on weighted or matched data approaches provides a flexible and robust method to correct for covariate imbalances in economic evaluations. The conclusions of our study may be generalizable to other settings.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT01568866 (ENDEAVOR trial).

Development of an Initial Conceptual Model of Multiple Myeloma to Support Clinical and Health Economics Decision Making

Background. We aimed to develop and validate a conceptual model of multiple myeloma (MM) that characterizes the attributes affecting disease progression and patient outcomes, and the relationships between them. Methods. Systematic and targeted literature reviews identified disease- and patient-specific attributes of MM that affect disease progression and outcomes. These attributes were validated by a Delphi panel of four international MM experts, and a physician-validated model was constructed. Real-world clinical data from the Czech Registry of Monoclonal Gammopathies (RMG) was used to confirm the relationships between attributes using pairwise correlations and multiple Cox regression analysis. Results. The Delphi panel reached consensus that most cytogenetic abnormalities influenced disease activity, which results in symptoms and complications and affects overall survival (OS). Comorbidities and complications also affect OS. The entire panel agreed that quality of life was influenced by comorbidities, age, complications, and symptoms. Consensus was not reached in some cases, in particular, the influence of del(17p) on complications. The relationships between attributes were confirmed using pairwise analysis of real-world data from the Czech RMG; most of the correlations identified were statistically significant and the strength of the correlations changed with successive relapses. Czech RMG data were also used to confirm significant predictors of OS included in the model, such as age, Eastern Cooperative Oncology Group performance status, and extramedullary disease. Conclusions. This validated conceptual model can be used for economic modeling and clinical decision making. It could also inform the development of disease-based models to explore the impact of disease progression and treatment on outcomes in patients with MM.

Cost-effectiveness of carfilzomib plus dexamethasone compared with bortezomib plus dexamethasone for patients with relapsed or refractory multiple myeloma in the United States

BACKGROUND

We assessed the economic value of carfilzomib 56 mg/m² and dexamethasone (Kd56) vs. bortezomib and dexamethasone (Vd) for relapsed/refractory multiple myeloma (R/RMM) using ENDEAVOR trial results.

METHODS

Cost-effectiveness of Kd56 vs. Vd was assessed using a partitioned survival model by estimating progression-free survival, overall survival, and direct costs over a lifetime horizon. Surveillance Epidemiology and End Results (SEER) survival data were extrapolated after matching registry and ENDEAVOR patients. Utilities were sourced from the literature and mapped from patient-reported quality of life in ENDEAVOR to estimate quality-adjusted life-years (QALYs) from life-years (LYs).

RESULTS

The model predicted an average gain of 1.66 LYs and 1.50 QALYs with Kd56 vs. Vd, and lifetime additional costs of $182,699, resulting in an incremental cost-effectiveness ratio (ICER) of $121,828/QALY gained. The ICER was $114,793/QALY in patients with 1 prior treatment; $99,263/QALY in those not transplanted, and <$150,000/QALY up to an 85% discount in bortezomib price.

CONCLUSIONS

Kd56 is cost-effective for patients with R/RMM at a willingness-to-pay threshold of $150,000/QALY. Trial data in the model may limit generalizability; however, SEER registry data mitigates this challenge. Kd56 provides additional value in key subgroups, and remains cost-effective after steep comparator discounts.

Cost per response analysis of strategies for chronic immune thrombocytopenia

OBJECTIVES

This analysis estimated the cost per response and the incremental cost per additional responder of romplostim, eltrombopag, and the "watch-and-rescue" (monitoring until rescue therapies are required) strategy in adults with chronic immune thrombocytopenia (ITP).

STUDY DESIGN

The decision tree is designed to estimate the total cost per response for romiplostim, eltrombopag, and watch and rescue over a 24-week time horizon; cost-effectiveness was evaluated in terms of incremental cost per additional responder.

METHODS

Model inputs including response rates, bleeding-related episode (BRE) rates, and costs were estimated from registrational trial data, an independent Bayesian indirect comparison, database analyses, and peer-reviewed publications. Costs were applied to the proportions of patients with treatment response and nonresponse (based on platelet count). The total cost per response and the incremental cost per additional responder for each treatment were calculated. Sensitivity analyses and alternative analyses were performed.

RESULTS

With higher total costs and greater treatment efficacy, romiplostim and eltrombopag had a lower 24-week cost per response and a lower average number of BREs than watch and rescue. Eltrombopag was weakly dominated by romiplostim. The incremental cost-effectiveness ratio of romiplostim versus watch and rescue was $46,000 per additional responder. The model results are most sensitive to response rates of romiplostim and watch and rescue and the BRE rate for splenectomized nonresponders. Alternative analyses results were similar to the base case.

CONCLUSIONS

In adults with chronic ITP, romiplostim represents an efficient way to achieve response, with lower costs per response than eltrombopag; both romiplostim and eltrombopag had lower costs per response than watch and rescue.

Reframing the Value of Treatments for Relapsed/Refractory Multiple Myeloma

DISCLOSURES

Ailawadhi reports research support from Pharmacyclics and consulting relationships with Takeda, Amgen, and Celgene. Jakubowiak reports consulting and advisory board relationships with AbbVie, Amgen, BMS, Celgene, Karyopharm, SkylineDX, and Takeda. Panjabi, Campioni, and Majer are employees of and stockholders in Amgen.

Healthcare resource utilization among patients with relapsed multiple myeloma in the UK, France, and Italy

AIMS

To assess the real-world healthcare resource utilization (HRU) and costs associated with different treatment regimens used in the management of patients with relapsed multiple myeloma in the UK, France, and Italy.

METHODS

Retrospective medical chart review of characteristics, time to progression, level of response, HRU during treatment, and adverse events (AEs). Data collection started on June 1, 2015 and was completed on July 15, 2015. In the 3 months before record abstraction, eligible patients had either disease progression after receiving one of their country's most commonly prescribed regimens or had received the best supportive care and died. Costs were calculated based on HRU and country-specific diagnosis-related group and/or unit reference costs, amongst other standard resources.

RESULTS

Physicians provided data for 1,282 patients (387 in the UK, 502 in France, 393 in Italy) who met the inclusion criteria. Mean [median] total healthcare costs associated with a single line of treatment were €51,717 [35,951] in the UK, €37,009 [32,538] for France, and €34,496 [42,342] for Italy, driven largely by anti-myeloma medications costs (contributing 95.0%, 90.0%, and 94.2% of total cost, respectively). During active treatment, the highest costs were associated with lenalidomide- and pomalidomide-based regimens. Mean cost per month was lowest for patients achieving a very good partial response or better. Unscheduled events (i.e. not considered part of routine management, whether or not related to multiple myeloma, such as unscheduled hospitalization, AEs, fractures) accounted for 1-9% of total costs and were highest for bendamustine.

LIMITATIONS

The use of retrospective data means that clinical practice (e.g. use of medical procedures, evaluation of treatment response) is not standardized across participating countries/centers, and some data (e.g. low-grade AEs) may be incomplete or differently adjudicated/reported. The centers involved may not be fully representative of national practice.

CONCLUSIONS

Drug costs are the main contributor to total HRU costs associated with multiple myeloma. The duration of active treatment may influence the average total costs, as well as response, associated with a single line of therapy. Improved treatment outcomes, and reductions in unscheduled events and concomitant medication use may, therefore, reduce the overall HRU and related costs of care in multiple myeloma.

Healthcare resource utilisation associated with skeletal-related events in European patients with multiple myeloma: Results from a prospective, multinational, observational study

OBJECTIVES

Patients with multiple myeloma (MM) often experience debilitating skeletal-related events (SREs: pathologic fracture, radiation to bone [RB], surgery to bone [SB] or spinal cord compression [SCC]). This is the first comprehensive, prospective, observational analysis of healthcare resource utilisation (HRU), independently attributed to SREs by investigators, in patients with MM.

METHODS

Eligible patients had lytic bone lesions, life expectancy ≥6 months, Eastern Cooperative Oncology Group performance status ≤2 and ≥1 SRE in the 97 days before enrolment. Data were collected retrospectively for 97 days before enrolment and prospectively for 18-21 months.

RESULTS

Altogether, 153 patients were enrolled from Germany, Italy, Spain and the United Kingdom. Of the 281 observed SREs, 36.7% required inpatient stays (mean duration: 20.6 days per SRE [standard deviation (SD): 22.9]). SB and SCC were the SREs most likely to require stays (72.3% and 50.0% of SREs, respectively); SCC required the longest mean (SD) stay per event (40.5 [40.8] days). Overall, 179 SREs required outpatient visits; this was most likely for RB (74.8%) and least likely for non-vertebral fracture (50.0%).

CONCLUSIONS

All SREs were associated with substantial HRU; therefore, preventing SREs in MM will reduce the economic and resource burden on healthcare systems.

Cost-effectiveness of adding carfilzomib to lenalidomide and dexamethasone in relapsed multiple myeloma from a US perspective

OBJECTIVE

To assess the economic value of carfilzomib (Kyprolis), this study developed the Kyprolis Global Economic Model (K-GEM), which examined from a United States (US) payer perspective the cost-effectiveness of carfilzomib-lenalidomide-dexamethasone (KRd) versus lenalidomide-dexamethasone (Rd) in relapsed multiple myeloma (RMM; 1-3 prior therapies) based on results from the phase III ASPIRE trial that directly compared these regimens.

METHODS

A partitioned survival model that included three health states of progression-free (on or off treatment), post-progression, and death was developed. Using ASPIRE data, the effect of treatment regimens as administered in the trial was assessed for progression-free survival and overall survival (OS). Treatment effects were estimated with parametric regression models adjusting for baseline patient characteristics and applied over a lifetime horizon. US Surveillance, Epidemiology and End Results (1984-2014) registry data were matched to ASPIRE patients to extrapolate OS beyond the trial. Estimated survival was adjusted to account for utilities across health states. The K-GEM considered the total direct costs (pharmacy/medical) of care for patients treated with KRd and Rd.

RESULTS

KRd was estimated to be more effective compared to Rd, providing 1.99 life year and 1.67 quality-adjusted life year (QALY) gains over the modeled horizon. KRd-treated patients incurred $179,393 in total additional costs. The incremental cost-effectiveness ratio (ICER) was $107,520 per QALY.

LIMITATIONS

Extrapolated survival functions present the greatest uncertainty in the modeled results. Utilities were derived from a combination of sources and assumed to reflect how US patients value their health state.

CONCLUSIONS

The K-GEM showed KRd is cost-effective, with an ICER of $107,520 per QALY gained against Rd for the treatment of patients with RMM (1-3 prior therapies) at a willingness-to-pay threshold of $150,000. Reimbursement of KRd for patients with RMM may represent an efficient allocation of the healthcare budget.

Visual Predictive Check in Models with Time-Varying Input Function

The nonlinear mixed effects models are commonly used modeling techniques in the pharmaceutical research as they enable the characterization of the individual profiles together with the population to which the individuals belong. To ensure a correct use of them is fundamental to provide powerful diagnostic tools that are able to evaluate the predictive performance of the models. The visual predictive check (VPC) is a commonly used tool that helps the user to check by visual inspection if the model is able to reproduce the variability and the main trend of the observed data. However, the simulation from the model is not always trivial, for example, when using models with time-varying input function (IF). In this class of models, there is a potential mismatch between each set of simulated parameters and the associated individual IF which can cause an incorrect profile simulation. We introduce a refinement of the VPC by taking in consideration a correlation term (the Mahalanobis or normalized Euclidean distance) that helps the association of the correct IF with the individual set of simulated parameters. We investigate and compare its performance with the standard VPC in models of the glucose and insulin system applied on real and simulated data and in a simulated pharmacokinetic/pharmacodynamic (PK/PD) example. The newly proposed VPC performance appears to be better with respect to the standard VPC especially for the models with big variability in the IF where the probability of simulating incorrect profiles is higher.

Population pharmacokinetics of cilengitide in adult and pediatric cancer patients from a nonlinear mixed-effects analysis

Cilengitide is an αvβ3/αvβ5-integrin inhibitor investigated as an anticancer agent. This study aimed to develop a cilengitide population pharmacokinetic model using nonlinear mixed-effects modeling of 136 adult patients with advanced solid tumors and to scale the pharmacokinetic parameters to the pediatric population. A stepwise approach was used, beginning with exploratory analyses checking database/target covariate relationships. A two-compartment structural model was developed to describe cilengitide's concentration-time profile and assess covariates' impact on pharmacokinetic parameters. A bootstrap procedure validated the base/final model stability. A two-compartment model best described concentration-time data. Estimated structural model parameters were: 2.79 L h(-) (1)  m(-) (2) central compartment mean systemic clearance, 6.75 L m(-) (2) central compartment volume of distribution, 1.3 L h(-) (1)  m(-) (2) intercompartmental clearance, and 3.85 L m(-) (2) peripheral compartment volume of distribution. Mean half-life was 0.9 and 3.8 h (α/β-phase). Co-medications and study populations had no impact, as the different studies were not significant model covariates. Weight and body surface area correlated with the pharmacokinetic parameters (r = 0.95, P < 0.01). Pharmacokinetic parameters were consistent with individual study-derived parameters; their allometric scaling enabled pediatric pharmacokinetic profile predictions as corroborated by independent data. This model provides the basis for pharmacokinetic profile simulations of different dosages/regimens in different populations.

Minimal model assessment of hepatic insulin extraction during an oral test from standard insulin kinetic parameters

In this article, a first aim was to develop a minimal modeling approach to noninvasively assess hepatic insulin extraction in 204 healthy subjects studied with a standard meal by coupling the already available meal C-peptide minimal model with a new insulin model. The ingredients of this model are posthepatic IDR, which in turn is described in terms of pancreatic ISR and hepatic insulin extraction HE, and a linear monocompartmental model of insulin kinetics. Even if ISR is provided by the C-peptide minimal model, the simultaneous assessment of HE and insulin kinetics is critical, since compensations may arise between parameters describing these two processes. Therefore, as a second aim of this study, a method was developed to predict standard values of insulin kinetic parameters in an individual on the basis of the individual's anthropometric characteristics. The statistical analysis, based on linear regression of insulin kinetic parameters estimated from IM-IVGTT data performed on the same subjects, demonstrated that insulin kinetic parameters can be accurately predicted from age and body surface area. Once kinetic parameters of the new insulin model were fixed to these values, HE profile and indexes during a meal were reliably estimated in each individual, indicating a significant suppression during the meal since the overall index of HE, equal to 60 +/- 1% in the basal state, is reduced to 40 +/- 1% during a meal. However, standard parameters provide an approximation of the individual one; thus, the third aim was to define the impact on estimated indexes of using standard instead of individually estimated values. Our results showed that the 25% uncertainty affecting as an average insulin kinetic parameters of an individual, when they are predicted from age and body surface area, translates into a similar relative uncertainty in the individual's hepatic insulin extraction indexes.

Short-term high dietary fructose intake had no effects on insulin sensitivity and secretion or glucose and lipid metabolism in healthy, obese adolescents

There is virtually no information on the metabolic impact of dietary fructose intake in adolescents despite their high fructose consumption, particularly via sweetened beverages.

AIM

To determine the short-term metabolic effects of dietary fructose intake in obese adolescents.

METHODS

Six volunteers (3 M/3 F; 15.2 +/- 0.5 yr; 35 +/- 2 kg/m2; 39 +/- 2% body fat) were studied twice following 7 d of isocaloric, isonitrogenous high carbohydrate (60% CHO; 25% fat) diets with fructose accounting for 6% and 24% of total energy intake, respectively (random order). Insulin sensitivity and secretion were analyzed by the stable labeled intravenous glucose tolerance test and glucose and lipid kinetics using GCMS.

RESULTS

A fourfold increase in dietary fructose intake did not affect insulin sensitivity or secretion, glucose kinetics, lipolysis or glucose, insulin, C-peptide, triglycerides, HDL- and LDL-cholesterol concentrations.

CONCLUSIONS

In the short term, when energy intake is constant, dietary fructose per se is not a contributor to insulin resistance and hypersecretion in obese adolescents.

Cell-cycle molecules in mesothelioma: an overview

Cell cycle progression is mediated by a group of proteins named cyclins that activate a highly conserved family of protein kinases, the cyclin-dependent kinases (CDKs). CDKs are also regulated by related proteins called cdk inhibitors, grouped into two families: the INK4 inhibitors (p16, p15, p19 and p18) and the Cip/Kip inhibitors (p21, p27). Moreover, several tumour suppressor genes (such as Retinoblastoma gene and p53 gene) are implicated in the regulation of the molecular mechanism of cell division. Several studies report the importance of cell cycle regulator proteins in the pathogenesis and the prognosis of mesothelioma. This article will review the most recent data from the literature about the expression and the diagnostic and prognostic significance of cell cycle molecules in mesothelioma.

Effect of 2 years of testosterone replacement on insulin secretion, insulin action, glucose effectiveness, hepatic insulin clearance, and postprandial glucose turnover in elderly men

OBJECTIVE

We sought to determine whether, and if so the mechanism by which, testosterone replacement improves carbohydrate tolerance.

RESEARCH DESIGN AND METHODS

Fifty-five elderly men with relative testosterone deficiency ingested a labeled mixed meal and underwent a frequently sampled labeled intravenous glucose tolerance test before and after either placebo or treatment with testosterone patch (5 mg/day) for 2 years.

RESULTS

Despite restoring bioavailable testosterone to values observed in young men, the change (24 months minus baseline values) in fasting and postprandial glucose, insulin, and C-peptide concentrations and meal appearance, glucose disposal, and endogenous glucose production were virtually identical to those observed after 2 years of placebo. The change over time in insulin and C-peptide concentrations post-intravenous glucose injection also did not differ. Furthermore, the change over time in insulin action and glucose effectiveness (measured with the unlabeled and labeled "oral" and "intravenous" minimal models), as well as insulin secretion and hepatic insulin clearance (measured with the C-peptide model), did not differ in the testosterone and placebo groups.

CONCLUSIONS

We conclude that 2 years of treatment with testosterone in elderly men does not improve carbohydrate tolerance or alter insulin secretion, insulin action, glucose effectiveness, hepatic insulin clearance, or the pattern of postprandial glucose metabolism. Thus, testosterone deficiency is unlikely the cause of the age-associated deterioration in glucose tolerance commonly observed in elderly men.

Assessment of beta-cell function in humans, simultaneously with insulin sensitivity and hepatic extraction, from intravenous and oral glucose tests

Assessment of insulin secretion in humans under physiological conditions has been a challenge because of its complex interplay with insulin action and hepatic insulin extraction. The possibility of simultaneously assessing beta-cell function, insulin sensitivity, and hepatic insulin extraction under physiological conditions using a simple protocol is appealing, since it has the potential to provide novel insights regarding the regulation of fasting and postprandial glucose metabolism in diabetic and nondiabetic humans. In this Perspective, we review data indicating that an oral glucose tolerance test (OGTT) or a meal test is able to accomplish this goal when interpreted with the oral beta-cell minimal model. We begin by using the well-established intravenous minimal model to highlight how the oral minimal model was developed and how the oral assessment parallels that of an intravenous glucose tolerance test (IVGTT). We also point out the unique aspects of both approaches in relation to their ability to assess different aspects of the beta-cell secretory cascade. We review the ability of the oral model to concurrently measure insulin sensitivity and hepatic insulin extraction, thereby enabling it to quantitatively portray the complex relationship among beta-cell function, hepatic insulin extraction, and insulin action. In addition, data from 204 individuals (54 young and 159 elderly) who underwent both IVGTT and meal tolerance tests are used to illustrate how these different approaches provide complementary but differing insights regarding the regulation of beta-cell function in humans.

Effects of nonglucose nutrients on insulin secretion and action in people with pre-diabetes

To determine whether nonglucose nutrient-induced insulin secretion is impaired in pre-diabetes, subjects with impaired or normal fasting glucose were studied after ingesting either a mixed meal containing 75 g glucose or 75 g glucose alone. Despite comparable glucose areas above basal, glucose-induced insulin secretion was higher (P < 0.05) and insulin action lower (P < 0.05) during the meal than the oral glucose tolerance test (OGTT) in all subgroups regardless of whether they had abnormal or normal glucose tolerance (NGT). However, the nutrient-induced delta (meal minus OGTT) in insulin secretion and glucagon concentrations did not differ among groups. Furthermore, the decrease in insulin action after meal ingestion was compensated in all groups by an appropriate increase in insulin secretion resulting in disposition indexes during meals that were equal to or greater than those present during the OGTT. In contrast, disposition indexes were reduced (P < 0.01) during the OGTT in the impaired glucose tolerance groups, indicating that reduced glucose induced insulin secretion. We conclude that, whereas glucose-induced insulin secretion is impaired in people with abnormal glucose tolerance, nonglucose nutrient-induced secretion is intact, suggesting that a glucose-specific defect in the insulin secretory pathway is an early event in the evolution of type 2 diabetes.

Two years of treatment with dehydroepiandrosterone does not improve insulin secretion, insulin action, or postprandial glucose turnover in elderly men or women

To determine if dehydroepiandrosterone (DHEA) replacement improves insulin secretion, insulin action, and/or postprandial glucose metabolism, 112 elderly subjects with relative DHEA deficiency ingested a labeled mixed meal and underwent a frequently sampled intravenous glucose tolerance test before and after 2 years of either DHEA or placebo. Despite restoring DHEA sulphate concentrations to values observed in young men and women, the changes over time in fasting and postprandial glucose concentrations, meal appearance, glucose disposal, and endogenous glucose production were identical to those observed after 2 years of placebo. The change over time in postmeal and intravenous glucose tolerance test insulin and C-peptide concentrations did not differ in men treated with DHEA or placebo. In contrast, postmeal and intravenous glucose tolerance test change over time in insulin and C-peptide concentrations were greater (P < 0.05) in women after DHEA than after placebo. However, since DHEA tended to decrease insulin action, the change over time in disposition indexes did not differ between DHEA- and placebo-treated women, indicating that the slight increase in insulin secretion was a compensatory response to a slight decrease in insulin action. We conclude that 2 years of replacement of DHEA in elderly men and women does not improve insulin secretion, insulin action, or the pattern of postprandial glucose metabolism.

Incretin effect potentiates beta-cell responsivity to glucose as well as to its rate of change: OGTT and matched intravenous study

The aim of this study is to gain greater insight into the mechanism whereby "incretins" (greater insulinemia after oral than intravenous glucose) enhance insulin secretion. To do so, we use a model of C-peptide secretion to reanalyze data from a previously published study in which glycemic profiles observed following glucose ingestion were matched in the same 10 subjects by means of an intravenous glucose infusion. We report that incretins increase insulin secretion by enhancing both the dynamic (to the rate of increase of glucose) and static (to given glucose concentration) response with an increase of 58% for the static (Phi(s) = 16.4 +/- 1.8 vs. 24.6 +/- 2.0 10(-9) min(-1), P = 0.01) and 63% for the dynamic (Phi(d) = 278 +/- 32 vs. 463 +/- 86 10(-9), P = 0.02) indexes. Since increases in the dynamic response to glucose are believed to be due to an increase in the rate of docking, and exocytosis of insulin containing granules and increases in the static response to glucose are believed to be caused by a shift in the sensitivity of the beta-cell to glucose, these results suggest that incretins may modulate more than one step in the beta-cell insulin secretory cascade.

Pathogenesis of pre-diabetes: mechanisms of fasting and postprandial hyperglycemia in people with impaired fasting glucose and/or impaired glucose tolerance

Thirty-two subjects with impaired fasting glucose (IFG) and 28 subjects with normal fasting glucose (NFG) ingested a labeled meal and 75 g glucose (oral glucose tolerance test) on separate occasions. Fasting glucose, insulin, and C-peptide were higher (P < 0.05) in subjects with IFG than in those with NFG, whereas endogenous glucose production (EGP) did not differ, indicating hepatic insulin resistance. EGP was promptly suppressed, and meal glucose appearance comparably increased following meal ingestion in both groups. In contrast, glucose disappearance (R(d)) immediately after meal ingestion was lower (P < 0.001) in subjects with IFG/impaired glucose tolerance (IGT) and IFG/diabetes but did not differ in subjects with IFG/normal glucose tolerance (NGT) or NFG/NGT. Net insulin action (S(i)) and insulin-stimulated glucose disposal (S(i)*) were reduced (P < 0.001, ANOVA) in subjects with NFG/IGT, IFG/IGT, and IFG/diabetes but did not differ in subjects with NFG/NGT or IFG/NGT. Defective insulin secretion also contributed to lower postprandial R(d) since disposition indexes were lower (P < 0.001, ANOVA) in subjects with NFG/IGT, IFG/IGT, and IFG/diabetes but did not differ in subjects with NFG/NGT and IFG/NGT. We conclude that postprandial hyperglycemia in individuals with early diabetes is due to lower rates of glucose disappearance rather than increased meal appearance or impaired suppression of EGP, regardless of their fasting glucose. In contrast, insulin secretion, action, and the pattern of postprandial turnover are essentially normal in individuals with isolated IFG.

Prediction of postprandial glycemic exposure: utility of fasting and 2-h glucose measurements alone and in combination with assessment of body composition, fitness, and strength

OBJECTIVE

To determine the best predictors of total postprandial glycemic exposure and peak glucose concentrations in nondiabetic humans.

RESEARCH DESIGN AND METHODS

Data from 203 nondiabetic volunteers who ingested a carbohydrate-containing mixed meal were analyzed.

RESULTS

Fasting glucose and insulin concentrations were poor predictors of postprandial glucose area above basal (R2 = approximately 0.07, P < 0.001). The correlation was stronger for 2-h glucose concentration (R2 = 0.55, P < 0.001) and improved slightly but significantly (P < 0.001) with the addition of fasting glucose, insulin, age, sex, and body weight to the model (r2 = 0.58). The 2-h glucose concentration also predicted the peak glucose concentration (R2 = 0.37, P < 0.001) with strength of the prediction increasing (P < 0.001) modestly with the addition of fasting glucose, insulin, age, sex, and body weight to the model (R2 = 0.48, P < 0.001). On the other hand, addition of measures of body function and composition did not improve prediction of total glycemic exposure or peak glucose concentration.

CONCLUSIONS

Isolated measures of fasting or 2-h glucose concentrations alone or in combination with more complex measures of body composition and function are poor predictors of postprandial glycemic exposure or peak glucose concentration. This may explain, at least in part, the weak and at times inconsistent relationship between these parameters and cardiovascular risk.

Bone marrow and sentinel lymph node biopsy in patients with breast cancer: from staging to ultrastaging?

Bone marrow (BM) biopsy has been suggested as an independent prognostic tool to improve staging in patients with breast cancer. Two hundred and ten consecutive patients operated for breast cancer from June 2000 to June 2005 who signed an informed consent were enrolled in this protocol. Patients underwent SLN biopsy, and lymph nodes were analysed with serial sections and stained with hematossilin-eosin and immunohistochemistry. At the end of the procedure a BM aspirate from the iliac crest was obtained and 5-10 cc of blood collected. A CEA specific nested reverse transcriptase (RT) polymerase chain reaction (PCR) assay was used to examine BM samples. Results were blinded to both patients and clinicians. The median age of the patients was 56 years (range 34-80), and the median tumor diameter 1,5 cm (range 0.2-4.5). BM aspirates were unsuccessful in ten patients, and RT-PCR was not technically feasible in seventeen women, leaving 183 patients available for analysis of results and follow up. SLN biopsy allowed diagnoses of occult metastases (micrometastases and isolated tumor cells) in 16% of patients (29/183). 25% of T1N0 patients (23/92), 35% of T2N0 patients (6/17), and 44% of N1-2 patients (32/72) were BM+ (p = 0.03). At a median follow up of 35 months 5/122 in the BM- group and 6/61 in the BM+ group have relapsed (p = 0.2), while 1/122 and 4/61 have died of disease (p = 0.04) In conclusion, ultrastaging of breast cancer patients may identify a substantial subgroup of patients N-/BM- who may not require adjuvant chemotherapy, as well as a subgroup N-/BM+ with a decreased survival who may need more aggressive therapies. Further follow-up is needed to confirm this hypothesis, and several studies are under way.

Effects of age and sex on postprandial glucose metabolism: differences in glucose turnover, insulin secretion, insulin action, and hepatic insulin extraction

To determine the effects of age and sex on the regulation of postprandial glucose metabolism, glucose turnover, insulin secretion, insulin action, and hepatic insulin extraction were concurrently measured in 145 healthy elderly (aged 70 +/- 1 years) and in 58 young (aged 28 +/- 1 years) men and women before and after ingestion of a mixed meal containing [1-(13)C]glucose. At the time of meal ingestion, [6-(3)H]glucose and [6,6-(2)H(2)]glucose were infused intravenously to enable concurrent measurement of the rates of postprandial endogenous glucose production (EGP), meal appearance, and glucose disappearance. Fasting and postprandial glucose concentrations were higher (P < 0.001) in both elderly women and elderly men compared with young individuals of the same sex. The higher postprandial glucose concentrations in the elderly than young women were caused by higher rates of meal appearance (P < 0.01) and slightly lower (P < 0.05) rates of glucose disappearance immediately after eating. In contrast, higher glucose concentrations in the elderly than young men were solely due to decreased (P < 0.001) glucose disappearance. Although postprandial glucose concentrations did not differ in elderly women and elderly men, rates of meal appearance and glucose disappearance rates both were higher (P < 0.001) in the women. Fasting EGP was higher (P < 0.05) in elderly than young subjects of both sexes and in women than men regardless of age. On the other hand, postprandial suppression of EGP was rapid all groups. Insulin action and secretion were lower (P < 0.001) in the elderly than young men but did not differ in the elderly and young women. This resulted in lower (P < 0.001) meal disposition indexes in elderly than young men but no difference in elderly and young women. Total meal disposition indexes were lower (P < 0.05) in elderly men than elderly women, indicating impaired insulin secretion, whereas disposition indexes were higher (P < 0.05) in young men than young women. Hepatic insulin clearance was greater (P < 0.001) in the elderly than young subjects of both sexes but did not differ between men and women regardless of age. In contrast, the ability of glucose to facilitate its own uptake (glucose effectiveness) was higher (P < 0.001) in women than men but did not differ in elderly and young subjects. Thus, age and sex impact on insulin secretion, insulin action, hepatic insulin extraction, and glucose effectiveness, resulting in substantial differences in the regulation of postprandial glucose metabolism in men and women and in elderly and young subjects.

A minimal model of insulin secretion and kinetics to assess hepatic insulin extraction

The liver is the principal site of insulin degradation, and assessing its ability to extract insulin is important to understand several pathological states. Noninvasive quantification of hepatic extraction (HE) in an individual requires comparing the profiles of insulin secretion (ISR) and posthepatic insulin delivery rate (IDR). To do this, we propose here the combined use of the classical C-peptide minimal model with a new minimal model of insulin delivery and kinetics. The models were identified on insulin-modified intravenous glucose tolerance test (IM-IVGTT) data of 20 healthy subjects. C-peptide kinetics were fixed to standard population values, whereas insulin kinetics were assessed in each individual, along with IDR parameters, thanks to the presence of insulin decay data observed after exogenous insulin administration. From the two models, profiles of ISR and IDR were predicted, and ISR and IDR indexes of beta-cell responsivity to glucose in the basal state, as well as during first- and second-phase secretion, were estimated. HE profile, obtained by comparing ISR and IDR profiles, showed a rapid suppression immediately after the glucose administration. HE indexes, obtained by comparing ISR and IDR indexes, indicated that the liver is able to extract 70 +/- 9% of insulin passing through it in the basal state and 54 +/- 14% during IM-IVGTT. In conclusion, insulin secretion, kinetics, and hepatic extraction can be reliably assessed during an IM-IVGTT by using insulin and C-peptide minimal models.

Two-hour seven-sample oral glucose tolerance test and meal protocol: minimal model assessment of beta-cell responsivity and insulin sensitivity in nondiabetic individuals

Highly informative yet simple protocols to assess insulin secretion and action would considerably enhance the quality of epidemiological and large-scale clinical trials. In an effort to develop such protocols, a 5-h, 11-sample oral glucose tolerance test (OGTT) was performed in 100 individuals and a 7-h, 21-sample meal in another 100. Plasma glucose, insulin, and C-peptide concentrations were measured. We show that virtually the same minimal model assessment of beta-cell responsivity (dynamic [Phi(d)] and static [Phi(s)]), insulin sensitivity (Si), and disposition index (DI) can be obtained with a reduced seven-sample 2-h protocol: Phi(d), reduced versus full: 871.50 vs. 873.32, r = 0.98 in OGTT and 494.88 vs. 477.99 10(-9), r = 0.91 in meal; Phi(s): 42.36 vs. 44.35, r = 0.88 in OGTT and 35.31 vs. 35.37 10(-9) min(-1), r = 0.90 in meal; Si: 24.33 vs. 22.77 10(-5) dl x kg(-1) x min(-1) per pmol/l, r = 0.89 in OGTT and 19.03 vs. 19.77 10(-5) dl x kg(-1) x min(-1) per pmol/l, r = 0.85 in meal; and DI: 1,282.26 vs. 1,273.23, r = 0.84 in OGTT and 726.92 vs. 776.97 10(-14) dl . kg(-1) x min(-2) per pmol/l, r = 0.84 in meal. This reduced protocol will facilitate the study of insulin secretion and action under physiological conditions in nondiabetic humans.

Effects of dietary macronutrient intake on insulin sensitivity and secretion and glucose and lipid metabolism in healthy, obese adolescents

CONTEXT

Adolescent obesity is a serious public health concern.

OBJECTIVE

The aim of the study was to determine whether obese adolescents can adapt metabolically to changes in dietary macronutrient intake.

PATIENTS AND DESIGN

Using a random cross-over design, 13 healthy obese volunteers (six boys and seven girls; age, 14.7 +/- 0.3 yr; body mass index, 34 +/- 1 kg/m2; body fat, 42 +/- 1%) were studied twice after 7 d of isocaloric, isonitrogenous diets with 60% carbohydrate (CHO) and 25% fat (high CHO), or 30% CHO and 55% fat (low CHO).

MAIN OUTCOME MEASURES AND METHODS

Glucose metabolism, insulin sensitivity, and first- and second-phase insulin secretory indices were measured by stable isotope techniques and the stable labeled iv glucose tolerance test. The results were compared with those of previously studied lean adolescents.

RESULTS

Obese adolescents increased first- and second-phase insulin secretory indices by 18 (P = 0.05) and 36% (P = 0.05), respectively, to maintain normoglycemia during the high-CHO diet because they failed to increase insulin sensitivity as did the lean adolescents. Regardless of diet, in obese adolescents, insulin sensitivity was half (P < 0.05) and first- and second-phase insulin secretory indices twice (P < 0.01), compared with the the corresponding values in lean subjects. In obese adolescents, gluconeogenesis increased by 32% during the low-CHO (high-fat diet) (P < 0.01).

CONCLUSION

In obese adolescents, insulin secretory demands were increased regardless of diet. Failure to increase insulin sensitivity while receiving a high-CHO diet required a further increase in insulin secretion, which may lead to earlier beta-cell failure. A low-CHO/high-fat diet resulted in increased gluconeogenesis, which may be a prelude to the increased glucose production and hyperglycemia observed in type 2 diabetics.

[The Urovac bladder evacuator: comparison with traditionally used devices]

Bladder evacuation device "Urovac": comparison with the conventional most used devices. We evaluated a new technique for bladder evacuation primarily during Turp using a disposable device called Urovac. This device proved to be better for evacuation of prostatic chips than both the Ellik evacuation and Toomey syringe.