Population pharmacokinetics of temozolomide in cancer patients

MGMT Methylation and Differential Survival Impact by Sex in Glioblastoma

Introduction: Sex differences in glioblastoma (GBM) have been observed in incidence, genetic and epigenetic alterations, and immune response. These differences have extended to the methylation of the MGMT promoter, which critically impacts temozolomide resistance. However, the association between sex, MGMT methylation, and survival is poorly understood, which this study sought to evaluate. Methods: A retrospective cohort study was conducted and reported following STROBE guidelines, based on adults with newly diagnosed GBM who received their first surgical intervention at Cleveland Clinic (Ohio, USA) between 2012 and 2018. Kaplan-Meier and multivariable Cox proportional hazards models were used to analyze the association between sex and MGMT promoter methylation status on overall survival (OS). MGMT was defined as methylated if the mean of CpG 1-5 ≥ 12. Propensity score matching was performed on a subset of patients to evaluate the effect of individual CpG site methylation. Results: A total of 464 patients had documented MGMT methylation status with a mean age of 63.4 (range 19-93) years. A total of 170 (36.6%) were female, and 133 (28.7%) received gross total resection as a first intervention. A total of 42.5% were MGMT methylated, with females more often having MGMT methylation than males (52.1% vs. 37.4%, p = 0.004). In univariable analysis, OS was significantly longer for MGMT promoter methylated than un-methylated groups for females (2 yr: 36.8% vs. 11.1%; median: 18.7 vs. 9.5 months; p = 0.001) but not for males (2 yr: 24.3% vs. 12.2%; median: 12.4 vs. 11.3 months; p = 0.22, p for MGMT-sex interaction = 0.02). In multivariable analysis, MGMT un-methylated versus methylated promoter females (2.07; 95% CI, 1.45-2.95; p < 0.0001) and males (1.51; 95% CI, 1.14-2.00; p = 0.004) had worse OS. Within the MGMT promoter methylated group, males had significantly worse OS than females (1.42; 95% CI: 1.01-1.99; p = 0.04). Amongst patients with data on MGMT CpG promoter site methylation values (n = 304), the median (IQR) of CpG mean methylation was 3.0% (2.0, 30.5). Females had greater mean CpG methylation than males (11.0 vs. 3.0, p < 0.002) and higher per-site CpG methylation with a significant difference at CPG 1, 2, and 4 (p < 0.008). After propensity score matching, females maintained a significant survival benefit (18.7 vs. 10.0 months, p = 0.004) compared to males (13.0 vs. 13.6 months, p = 0.76), and the pattern of difference was significant (P for CpG-sex interaction = 0.03). Conclusions: In this study, females had higher mean and individual CpG site methylation and received a greater PFS and OS benefit by MGMT methylation that was not seen in males despite equal degrees of CpG methylation.

A Multicenter Randomized Bioequivalence Study of a Novel Ready-to-Use Temozolomide Oral Suspension vs. Temozolomide Capsules

BACKGROUND

Temozolomide (TMZ) oral suspension (Ped-TMZ, KIZFIZO®) is being developed for the treatment of relapsed or refractory neuroblastoma, a rare cancer affecting infants and young children. The study assessed the safety and the bioequivalence of this novel pediatric formulation with existing TMZ oral capsules.

METHODS

In vitro dissolution profiles and the bioequivalence were evaluated following the European Medicines Agency "Guidelines on the investigation of Bioequivalence". The phase I, multicenter, randomized, open-label, crossover, single-dose bioequivalence study enrolled 36 adult patients with glioblastoma multiforme or lower-grade glioma. Each patient received 200 mg/m2 Ped-TMZ suspension and TMZ capsules (Temodal®) on 2 consecutive days, with the order being randomly assigned. Fourteen blood samples were collected up to 10 h post-dosing. Bioequivalence was assessed by comparing the 90% confidence interval for the ratio of the geometric means of maximum TMZ plasma concentration (Cmax) and the area under the curve (AUCt). Other endpoints included further pharmacokinetic parameters and safety.

RESULTS

Both formulations exhibited a fast in vitro dissolution profile with more than 85% of TMZ dissolved within 15 min. For the bioequivalence study, thirty patients completed the trial as per the protocol. The ratio of Ped-TMZ/TMZ capsule geometric means (90% CI) for AUCt and Cmax were 97.18% (95.05-99.35%) and 107.62% (98.07-118.09%), respectively, i.e., within the 80-125% bioequivalence limits. No buccal toxicity was associated with Ped-TMZ liquid formulation.

CONCLUSIONS

This study showed that Ped-TMZ oral suspension and TMZ oral capsule treatment are immediate release and bioequivalent medicines. There were also no unexpected safety signals or local toxicity (funded by ORPHELIA Pharma; ClinicalTrials.gov number, NCT04467346).

Myelotoxicity of Temozolomide Treatment in Patients with Glioblastoma Is It Time for a More Mechanistic Approach?

Glioblastoma multiforme is the most common primary central nervous system tumor, with an incidence of 3 [...].

Reinforcement learning for optimal scheduling of Glioblastoma treatment with Temozolomide

BACKGROUND

Glioblastoma multiforme (GBM) is the most frequent primary brain tumor in adults and Temozolomide (TMZ) is an effective chemotherapeutic agent for its treatment. In Silico models of GBM growth provide an appropriate foundation for analysis and comparison of different regimens. We propose a mathematical frame for patient specific design of optimal chemotherapy regimens for GBM patients.

METHODS

The proposed frame includes online interaction of a virtual GBM with an optimizing agent. Spatiotemporal dynamics of GBM growth and its response to TMZ are simulated with a three dimensional hybrid cellular automaton. Q learning is tailored to the virtual GBM for treatment optimization aimed at minimizing tumor size at the end of treatment course. Q learning consists of a learning agent that interacts with the virtual GBM. System state is affected by the agent decisions and the obtained rewards guide Q learning to the optimal schedule.

RESULTS

Computational results confirm that the optimal chemotherapy schedule depends on some patient specific parameters including body weight, tumor size and its position in the brain. Furthermore, the algorithm is used for scheduling 2100 mg of TMZ on a virtual GBM and the obtained schedule is to administer150 mg of TMZ every other day. The obtained schedule is compared to the standard 7/14 regimen and the results show that it is superior to the 7/14 regimen in minimizing tumor size.

CONCLUSION

The proposed frame is an appropriate decision support system for patient specific design of TMZ administration regimens on GBM patients. Also, since the obtained optimal schedule outperforms the standard 7/14 regimen, it is worthy of further clinical testing.

Gender medicine and oncology: report and consensus of an ESMO workshop

BACKGROUND

The importance of sex and gender as modulators of disease biology and treatment outcomes is well known in other disciplines of medicine, such as cardiology, but remains an undervalued issue in oncology. Considering the increasing evidence for their relevance, European Society for Medical Oncology decided to address this topic and organized a multidisciplinary workshop in Lausanne, Switzerland, on 30 November and 1 December 2018.

DESIGN

Twenty invited faculty members and 40 selected physicians/scientists participated. Relevant content was presented by faculty members on the basis of a literature review conducted by each speaker. Following a moderated consensus session, the final consensus statements are reported here.

RESULTS

Clinically relevant sex differences include tumour biology, immune system activity, body composition and drug disposition and effects. The main differences between male and female cells are sex chromosomes and the level of sexual hormones they are exposed to. They influence both local and systemic determinants of carcinogenesis. Their effect on carcinogenesis in non-reproductive organs is largely unknown. Recent evidence also suggests differences in tumour biology and molecular markers. Regarding body composition, the difference in metabolically active, fat-free body mass is one of the most prominent: in a man and a woman of equal weight and height, it accounts for 80% of the man's and 65% of the woman's body mass, and is not taken into account in body-surface area based dosing of chemotherapy.

CONCLUSION

Sex differences in cancer biology and treatment deserve more attention and systematic investigation. Interventional clinical trials evaluating sex-specific dosing regimens are necessary to improve the balance between efficacy and toxicity for drugs with significant pharmacokinetic differences. Especially in diseases or disease subgroups with significant differences in epidemiology or outcomes, men and women with non-sex-related cancers should be considered as biologically distinct groups of patients, for whom specific treatment approaches merit consideration.

Potential effects of nicotine on glioblastoma and chemoradiotherapy: a review

Introduction: Glioblastoma multiforme (GBM) has a poor prognosis despite maximal surgical resection with subsequent multi-modal radiation and chemotherapy. Use of tobacco products following diagnosis and during the period of treatment for non-neural tumors detrimentally affects treatment and prognosis. Approximately, 16-28% of patients with glioblastoma continue to smoke after diagnosis and during treatment. The literature is sparse for information-pertaining effects of smoking and nicotine on GBM treatment and prognosis. Areas covered: This review discusses cellular pathways involved in GBM progression that might be affected by nicotine, as well as how nicotine may contribute to resistance to treatment. Similarities of GBM pathways to those in non-neural tumors are investigated for potential effects by nicotine. English language papers were identified using PubMed, Medline and Scopus databases using a combination of keywords including but not limited to the following: nicotine, vaping, tobacco, e-cigarettes, smoking, vaping AND glioblastoma or brain cancer OR/AND temozolomide, carmustine, methotrexate, procarbazine, lomustine, vincristine, and neural tumor cell lines. Expert opinion: Understanding the impact of nicotine on treatment and resistance to chemotherapeutics should allow physicians to educate their patients with GBM with evidence-based recommendations about the effects of continuing to use nicotine-containing products after diagnosis and during treatment.

Comparison of Temozolomide-Capecitabine to 5-Fluorouracile-Dacarbazine in 247 Patients with Advanced Digestive Neuroendocrine Tumors Using Propensity Score Analyses

INTRODUCTION

Although chemotherapy combining 5-fluorouracil (5FU)-dacarbazine (DTIC) or temozolomide (TEM)-capecitabine (CAP) is extensively used in patients with neuroendocrine tumors (NET), they were never compared. We compared their tolerance and efficacy in advanced NET.

METHODS

We evaluated the records of consecutive patients with pancreatic or small-intestine advanced NET who received 5FU-DTIC or TEM-CAP between July 2004 and December 2017 in 5 French centers. Tolerance, tumor response and progression-free survival (PFS) were compared. Factors associated with PFS were analyzed using Cox multivariate regression model. To reduce the confounding bias of the nonrandomized design, PFS was compared using propensity score analyses.

RESULTS

Ninety-four (5FU-DTIC) patients and 153 (TEM-CAP) patients were included. Pancreatic NET represented 82.3% of cases and 17.1, 61.8 and 10.9% of patients had G1, G2 or G3 NET respectively. Progression at baseline was reported in 92.7% of patients with available data. Grades 3-4 adverse events occurred in 24.7 and 8.5% of TEM-CAP and 5FU-DTIC patients respectively (p = 0.002). The overall response rate was 38.3 and 39.2% respectively (p = 0.596). Median PFS on raw analysis was similar to 5FU-DTIC and TEM-CAP (13.9 vs. 18.3 months, respectively p = 0.86). TEM-CAP was associated with an increased risk of progression on the raw multivariate analysis (hazard ratio [HR] 1.90, 95% CI [1.32-2.73], p = 0.001) and when adjusted on propensity score (HR 1.65, 95% CI [1.18-2.31], p = 0.004).

CONCLUSION

PFS may be longer with 5FU-DTIC than TEM-CAP in patients with advanced NET. Although patients often prefer oral chemotherapy, 5FU-DTIC is a relevant alternative. A randomized comparison is needed to confirm these results.

The Prognostic Roles of Gender and O6-Methylguanine-DNA Methyltransferase Methylation Status in Glioblastoma Patients: The Female Power

BACKGROUND

Clinical and molecular factors are essential to define the prognosis in patients with glioblastoma (GBM). O6-methylguanine-DNA methyltransferase (MGMT) methylation status, age, Karnofsky Performance Status (KPS), and extent of surgical resection are the most relevant prognostic factors. Our investigation of the role of gender in predicting prognosis shows a slight survival advantage for female patients.

METHODS

We performed a prospective evaluation of the Project of Emilia Romagna on Neuro-Oncology (PERNO) registry to identify prognostic factors in patients with GBM who received standard treatment.

RESULTS

A total of 169 patients (99 males [58.6%] and 70 females [41.4%]) were evaluated prospectively. MGMT methylation was evaluable in 140 patients. Among the male patients, 36 were MGMT methylated (25.7%) and 47 were unmethylated (33.6%); among the female patients, 32 were methylated (22.9%) and 25 were unmethylated (17.9%). Survival was longer in the methylated females compared with the methylated males (P = 0.028) but was not significantly different between the unmethylated females and the unmethylated males (P = 0.395). In multivariate analysis, gender and MGMT methylation status considered together (methylated females vs. methylated males; hazard ratio [HR], 0.459; 95% confidence interval [CI], 0.242-0.827; P = 0.017), age (HR, 1.025; 95% CI, 1.002-1.049; P = 0.032), and KPS (HR, 0.965; 95% CI, 0.948-0.982; P < 0.001) were significantly correlated with survival.

CONCLUSIONS

Survival was consistently longer among MGMT methylated females compared with males. Gender can be considered as a further prognostic factor.

A Model to Predict the Feasibility of Concurrent Chemoradiotherapy With Temozolomide in Glioblastoma Multiforme Patients Over Age 65

OBJECTIVES

It is controversial whether concurrent chemoradiotherapy (CRT) with temozolomide is feasible and beneficial in elderly patients with glioblastoma.

MATERIALS AND METHODS

Retrospective analysis of 74 elderly glioblastoma patients (65 y and above) treated with concurrent CRT with temozolomide. Factors influencing prognosis and feasibility of CRT were investigated.

RESULTS

The median overall survival was 11.3 months. Univariate analysis showed a significant difference in median overall survival for cumulative dose of concurrent temozolomide (optimal cutoff, 2655 mg/m; 13.9 mo for >2655 mg/m vs. 4.9 mo for ≤2655 mg/m; P=0.0216, adjusted for multiple testing). Furthermore, cumulative dose of concurrent temozolomide >2655 mg/m was a significant independent prognostic parameter in multivariate analysis (hazard ratio, 0.33; P=0.002). Hematotoxicity was the most common cause of treatment interruption or discontinuation in patients with an insufficient cumulative temozolomide dose. Prognostic factors for successful performance of CRT with a cumulative dose of concurrent temozolomide >2655 mg/m were female sex (odds ratio [OR], 0.174; P=0.006), age (OR, 0.826 per year; P=0.017), and pretreatment platelet count (OR, 1.013 per 1000 platelets/µL; P=0.001). For easy clinical application of the model an online calculator was developed, which is available at http://www.OldTMZ.com.

CONCLUSIONS

The probability of successful performance of concurrent CRT with temozolomide can be estimated based on the patient's age, sex, and pretreatment platelet count using the model developed in this study. Thus, a subgroup of elderly glioblastoma patients suitable for chemoradiation with temozolomide can be identified.

Pharmacokinetics of Chemotherapy in the Older Patient

Background

The number of individuals aged 65 years and older is growing rapidly, and the majority of cancers are diagnosed in this age group. Age-related changes in physiology can affect chemotherapy pharmacokinetics and pharmacodynamics in older patients.

Methods

We review the literature regarding the impact of age on the pharmacokinetics of commonly used chemotherapy drugs and discuss age-related changes in physiology and pharmacology that can affect chemotherapy tolerance in older patients.

Results

The data on age-related changes in chemotherapy pharmacokinetics are conflicting. While a few studies report age-related differences in chemotherapy pharmacokinetics, most found no significant difference or subtle differences in pharmacokinetics with aging. A difference in pharmacodynamics was commonly seen, however, with older patients at increased risk of myelosuppression and toxicity from age-related decline in organ function. The majority of these studies were performed in a small cohort of patients, thus limiting the generalizability of these results.

Conclusions

Additional studies are needed to address the pharmacokinetics and pharmacodynamics of cancer therapies in the older patient. Multicenter pharmacokinetic studies of adequate sample size, which include a thorough evaluation of physiologic factors and geriatric assessment parameters, would provide further insight into the factors affecting treatment tolerance. These studies would also help to guide appropriate chemotherapy dosing and interventions in order to maximize efficacy and minimize toxicity in the older patient.

Pharmacotherapy of Glioblastoma: Established Treatments and Emerging Concepts

Glioblastoma is the most frequent malignant brain tumor and is characterized by poor prognosis, increased invasiveness, and high recurrence rates. Standard treatment for glioblastoma includes maximal safe surgical resection, radiation, and chemotherapy with temozolomide. Despite treatment advances, only 15-20% of glioblastoma patients survive to 5 years, and no therapies have demonstrated a durable survival benefit in recurrent disease. In the last 10 years, significant advances in knowledge of the biology and molecular pathology of the malignancy have opened the way to new treatment options. Clinical management of patients (pseudo-progressions, side effects of therapies, best supportive care, centralization in expertise care centers) has improved. In brain tumors, such as in other solid tumors, we have entered an era of immune-oncology. Immunotherapy seems to have an acceptable safety and tolerability profile in the recurrent setting and is under investigation in clinical trials in newly diagnosed glioblastoma patients. This review focuses on novel targeted therapies recently developed for the management of newly diagnosed and recurrent glioblastomas.

Metronomic and metronomic-like therapies in neuroendocrine tumors - Rationale and clinical perspectives

Metronomic therapy is characterized by the administration of regular low doses of certain drugs with very low toxicity. There have been numerous debates over the empirical approach of this regimen, but fewest side effects are always something to consider in order to improve patients' quality of life. Neuroendocrine tumors (NETs) are rare malignancies relatively slow-growing; therefore their treatment is often chronic, involving several different therapies for tumor growth control. Knowing that these tumors are highly vascularized, the anti-angiogenic aspect is highly regarded as something to be targeted in all patients harboring NETs. Additionally the metronomic schedule has proved to be effective on an immunological level, rendering this approach as a multi-targeted therapy. Rationalizing that advanced NETs are in many cases a chronic disease, with which patients can live for as long as possible, a systemic therapy with regular low doses and a very low toxicity is in many cases a judicious manner of pursuing stabilization. Metronomic schedule is usually correlated with chemotherapy in oncology, but other therapies, such as radiotherapy and biotherapy can be delivered in a metronomic like manner. This review describes clinical trials and case series involving metronomic therapies alone or in combination in patients with advanced NETs. Nowadays level of evidence about metronomic therapy in NETs is quite low, therefore future prospective clinical studies are needed to validate the metronomic approach in specific clinical settings.

Improved survival for elderly married glioblastoma patients : Better treatment delivery, less toxicity, and fewer disease complications

OBJECTIVES

Marital status is a well-described prognostic factor in patients with gliomas but the observed survival difference is unexplained in the available population-based studies.

METHODS

A series of 57 elderly glioblastoma patients (≥70 years) were analyzed retrospectively. Patients received radiotherapy or chemoradiation with temozolomide. The prognostic significance of marital status was assessed. Disease complications, toxicity, and treatment delivery were evaluated in detail.

RESULTS

Overall survival was significantly higher in married than in unmarried patients (median, 7.9 vs. 4.0 months; p = 0.006). The prognostic significance of marital status was preserved in the multivariate analysis (HR, 0.41; p = 0.011). Married patients could receive significantly higher daily temozolomide doses (mean, 53.7 mg/m² vs. 33.1 mg/m²; p = 0.020), were more likely to receive maintenance temozolomide (45.7 % vs. 11.8 %; p = 0.016), and had to be hospitalized less frequently during radiotherapy (55.0 % vs. 88.2 %; p = 0.016). Of the patients receiving temozolomide, married patients showed significantly lower rates of hematologic and liver toxicity. Most complications were infectious or neurologic in nature. Complications of any grade were more frequent in unmarried patients (58.8 % vs. 30.0 %; p = 0.041) with the incidence of grade 3-5 complications being particularly elevated (47.1 % vs. 15.0 %; p = 0.004).

CONCLUSION

We found poorer treatment delivery as well as an unexpected severe increase in toxicity and disease complications in elderly unmarried glioblastoma patients. Marital status may be an important predictive factor for clinical decision-making and should be addressed in further studies.

Temozolomide and other potential agents for the treatment of glioblastoma multiforme

This article provides historical and recent perspectives related to the use of temozolomide for the treatment of glioblastoma multiforme. Temozolomide has quickly become part of the standard of care for the modern treatment of stage IV glioblastoma multiforme since its approval in 2005. Yet despite its improvements from previous therapies, median survival remains approximately 15 months, with a 2-year survival rate of 8% to 26%. The mechanism of action of this chemotherapeutic agent, conferred advantages and limitations, treatment resistance and rescue, and potential targets of future research are discussed.

Covariate pharmacokinetic model building in oncology and its potential clinical relevance

When modeling pharmacokinetic (PK) data, identifying covariates is important in explaining interindividual variability, and thus increasing the predictive value of the model. Nonlinear mixed-effects modeling with stepwise covariate modeling is frequently used to build structural covariate models, and the most commonly used software-NONMEM-provides estimations for the fixed-effect parameters (e.g., drug clearance), interindividual and residual unidentified random effects. The aim of covariate modeling is not only to find covariates that significantly influence the population PK parameters, but also to provide dosing recommendations for a certain drug under different conditions, e.g., organ dysfunction, combination chemotherapy. A true covariate is usually seen as one that carries unique information on a structural model parameter. Covariate models have improved our understanding of the pharmacology of many anticancer drugs, including busulfan or melphalan that are part of high-dose pretransplant treatments, the antifolate methotrexate whose elimination is strongly dependent on GFR and comedication, the taxanes and tyrosine kinase inhibitors, the latter being subject of cytochrome p450 3A4 (CYP3A4) associated metabolism. The purpose of this review article is to provide a tool to help understand population covariate analysis and their potential implications for the clinic. Accordingly, several population covariate models are listed, and their clinical relevance is discussed. The target audience of this article are clinical oncologists with a special interest in clinical and mathematical pharmacology.

Overcoming the challenges in the effective delivery of chemotherapies to CNS solid tumors

Locoregional therapies, such as surgery and intratumoral chemotherapy, do not effectively treat infiltrative primary CNS solid tumors and multifocal metastatic solid tumor disease of the CNS. It also remains a challenge to treat such CNS malignant solid tumor disease with systemic chemotherapies, although these lipid-soluble small-molecule drugs demonstrate potent cytotoxicity in vitro. Even in the setting of a 'normalized' tumor microenvironment, small-molecule drugs do not accumulate to effective concentrations in the vast majority of tumor cells, which is due to the fact that small-molecule drugs have short blood half-lives. It has been recently shown that drug-conjugated spherical lipid-insoluble nanoparticles within the 7-10 nm size range can deliver therapeutic concentrations of drug fraction directly into individual tumor cells following systemic administration, since these functionalized particles maintain peak blood concentrations for several hours and are smaller than the physiologic upper limit of pore size in the VEGF-derived blood capillaries of solid tumors, which is approximately 12 nm. In this article, the physiologic and ultrastructural basis of this novel translational approach for the treatment of CNS, as well as non-CNS, solid cancers is reviewed.

Impact of age, sex, and comorbidity on cancer therapy and disease progression

A theme of personalized medicine was highlighted at the 2009 Annual Meeting of the American Society of Clinical Oncology. To this end, the current review focuses on the impact of host characteristics (such as age, sex, and comorbidity) as they pertain to cancer biology, treatment efficacy, and tolerance. Increasing age is associated with complex changes in physiology, including alterations in renal and hepatic function, and decreased bone marrow reserve. These may in turn result in alterations in pharmacokinetics and toxicity related to many commonly used anticancer agents. Using tools, such as the geriatric assessment, may help to elucidate the physiologic age of the patient as opposed to the chronologic age. Increasing age is paralleled by an increase in comorbidity, and comorbidity may have independent prognostic implications and substantially impact medical decision making in the patient with cancer. Numerous biologic ties between cancer and comorbidity exist, one example being an association of diabetes with an increased risk of disease recurrence and mortality in the setting of colon cancer. Biologic features can also vary by sex; several biomarkers with either prognostic or predictive value (ie, excisionrepair cross-complementation group 1 expression, epidermal growth factor receptor mutation, or dihydropyrimidine dehydrogenase polymorphism) may differentiate efficacy or toxicity in males and females. Taken together, age, sex, and comorbidity each encompass a complex array of physiologic and molecular variations that may each aid in personalizing care for the patient with cancer.

Evaluation of the exposure equivalence of oral versus intravenous temozolomide

Purpose

Oral temozolomide is approved in many countries for malignant glioma and for melanoma in some countries outside the USA. This study evaluated the exposure equivalence and safety of temozolomide by intravenous infusion and oral administration.

Methods

Subjects with primary central nervous system malignancies (excluding central nervous system lymphoma) received 200 mg/m² of oral temozolomide on days 1, 2 and 5. On days 3 and 4, subjects received 150 mg/m² temozolomide either as a 90-min intravenous infusion on one day or by oral administration on an alternate day.

Results

Ratio of log-transformed means (intravenous:oral) of area under the concentration–time curve and maximum concentration of drug after dosing for temozolomide and 5-(3-methyltriazen-1-yl)imidazole-4-carboxamide (MTIC) met exposure equivalence criteria (90% confidence interval = 0.8–1.25). Treatment-emergent adverse events were consistent with those reported previously in subjects with recurrent glioma treated with oral temozolomide, except for mostly mild and transient injection site reactions with intravenous administration.

Conclusions

This study demonstrated an exposure equivalence of a 90-min intravenous infusion of temozolomide and an equivalent oral dose.

Clinical pharmacology of cancer therapies in older adults

This abbreviated review outlines the physiologic changes associated with aging, and examines how these changes may affect the pharmacokinetics and pharmacodynamics of anticancer therapies. We also provide an overview of studies that have been conducted evaluating the pharmacology of anticancer therapies in older adults, and issue a call for further research.

A spatiotemporal, patient individualized simulation model of solid tumor response to chemotherapy in vivo: the paradigm of glioblastoma multiforme treated by temozolomide

A novel four-dimensional, patient-specific Monte Carlo simulation model of solid tumor response to chemotherapeutic treatment in vivo is presented. The special case of glioblastoma multiforme treated by temozolomide is addressed as a simulation paradigm. Nevertheless, a considerable number of the involved algorithms are generally applicable. The model is based on the patient's imaging, histopathologic and genetic data. For a given drug administration schedule lying within acceptable toxicity boundaries, the concentration of the prodrug and its metabolites within the tumor is calculated as a function of time based on the drug pharamacokinetics. A discretization mesh is superimposed upon the anatomical region of interest and within each geometrical cell of the mesh the most prominent biological "laws" (cell cycling, necrosis, apoptosis, mechanical restictions, etc.) are applied. The biological cell fates are predicted based on the drug pharmacodynamics. The outcome of the simulation is a prediction of the spatiotemporal activity of the entire tumor and is virtual reality visualized. A good qualitative agreement of the model's predictions with clinical experience supports the applicability of the approach. The proposed model primarily aims at providing a platform for performing patient individualized in silico experiments as a means of chemotherapeutic treatment optimization.

A new approach to modeling covariate effects and individualization in population pharmacokinetics-pharmacodynamics

By combining Laplace's approximation and Monte Carlo methods to evaluate multiple integrals, this paper develops a new approach to estimation in nonlinear mixed effects models that are widely used in population pharmacokinetics and pharmacodynamics. Estimation here involves not only estimating the model parameters from Phase I and II studies but also using the fitted model to estimate the concentration versus time curve or the drug effects of a subject who has covariate information but sparse measurements. Because of its computational tractability, the proposed approach can model the covariate effects nonparametrically by using (i) regression splines or neural networks as basis functions and (ii) AIC or BIC for model selection. Its computational and statistical advantages are illustrated in simulation studies and in Phase I trials.

Simulating chemotherapeutic schemes in the individualized treatment context: the paradigm of glioblastoma multiforme treated by temozolomide in vivo

A novel patient individualized, spatiotemporal Monte Carlo simulation model of tumor response to chemotherapeutic schemes in vivo is presented. Treatment of glioblastoma multiforme by temozolomide is considered as a paradigm. The model is based on the patient's imaging, histopathologic and genetic data. A discretization mesh is superimposed upon the anatomical region of interest and within each geometrical cell of the mesh the most prominent biological "laws" (cell cycling, apoptosis, etc.) in conjunction with pharmacokinetics and pharmacodynamics information are applied. A good qualitative agreement of the model's predictions with clinical experience supports the applicability of the approach to chemotherapy optimization.

Phase I study of temozolomide plus paclitaxel in patients with advanced malignant melanoma and associated in vitro investigations

The purpose of this study was to determine activity of temozolomide combined with paclitaxel or epothilone B in vitro, and to investigate the combination of temozolomide with paclitaxel in a Phase I clinical trial. Melanoma cell lines A375P and DX3 were treated with temozolomide and either paclitaxel or epothilone B. Combination indices were determined to assess the degree of synergism. In a clinical study, 21 patients with malignant melanoma were treated with increasing doses of temozolomide (orally, days 1–5), in combination with a fixed dose of paclitaxel (i.v. infusion day 1), followed by dose escalation of the latter drug. Cycles of treatment were repeated every 3 weeks. Pharmacokinetics of both agents were determined on day 1, with temozolomide pharmacokinetics also assessed on day 5. All three compounds were active against the melanoma cell lines, with epothilone B being the most potent. There was a strong degree of synergism between temozolomide and either paclitaxel or epothilone B. In the clinical study, no pharmacokinetic interaction was observed between temozolomide and paclitaxel. Dose escalation of both drugs to clinically active doses was possible, with no dose-limiting toxicities observed at 200 mg m⁻² day⁻¹ temozolomide and 225 mg m⁻² day⁻¹ paclitaxel. There were two partial responses out of 15 evaluable patients. One patient remains alive and symptom-free at 4 years after treatment. Temozolomide and paclitaxel may be administered safely at clinically effective doses. Further evaluation of these combinations in melanoma is warranted.

Development of a pharmacokinetic limited sampling model for temozolomide and its active metabolite MTIC

PURPOSE

To develop a pharmacokinetic limited sampling model (LSM) for temozolomide and its metabolite MTIC in infants and children.

METHODS

LSMs consisting of either two or four samples were determined using a modification of the D-optimality algorithm. This accounted for prior distribution of temozolomide and MTIC pharmacokinetic parameters based on full pharmacokinetic sampling from 38 patients with 120 pharmacokinetic studies (dosage range 145-200 mg/m(2) per day orally). Accuracy and bias of each LSM were determined relative to the full sampling method. We also assessed the predictive performance of the LSMs using Monte-Carlo simulations.

RESULTS

The four strategies generated from the D-optimality algorithm were as follows: LSM 1=0.25, 1.25, and 3 h; LSM 2=0.25, 1.25, and 6 h; LSM 3=0.25, 0.5, 1.25, and 3 h; LSM 4=0.25, 0.5, 1.25, and 6 h. LSM 2 demonstrated the best combination of low bias [0.1% (-8.9%, 11%) and 11% (4.3%, 15%)] and high accuracy [-1.0% (-12%, 24%) and 14% (7.9%, 37%)] for temozolomide clearance and MTIC AUC, respectively. Furthermore, adding a fourth sample (e.g., LSM 4) did not substantially decrease the bias or increase the accuracy for temozolomide clearance or MTIC AUC. Results from Monte-Carlo simulations also revealed that LSM 2 had the best combination of lowest bias (0.1+/-6.1% and -0.8+/-6.5%), and the highest accuracy (4.5+/-4.1% and 5.0+/-4.3%) for temozolomide clearance and MTIC apparent clearance, respectively.

CONCLUSIONS

Using data derived from our population analysis, the sampling times for a limited sample pharmacokinetic model for temozolomide and MTIC in children are prior to the temozolomide dose, and 15 min, 1.25 h and 6 h after the dose.

Temozolomide in patients with advanced cancer: phase I and pharmacokinetic study

STUDY OBJECTIVE

To determine the maximum tolerated dose, dose-limiting toxicity, pharmacokinetics, and potential antitumor activity of temozolomide administered as a single dose every 28 days.

DESIGN

Open label, phase I, dose-escalation trial.

SETTING

University-affiliated cancer center.

PATIENTS

Eleven patients aged 33-73 years with a documented solid tumor or lymphoma who failed therapy of proven efficacy for their disease or had a disease for which no conventional therapy was available.

INTERVENTION

Temozolomide 500 mg/m2 was administered as a single oral dose every 28 days. Doses were escalated to 750 or 1000 mg/m2. No intrapatient dose escalation was allowed. At least two patients were enrolled at each dose level. Patients who did not have progressive disease and did not experience a dose-limiting toxicity, or experienced a dose-limiting toxicity but were eligible for dose reduction, were eligible to continue on the study.

MEASUREMENTS AND MAIN RESULTS

Pharmacokinetic analysis was performed for temozolomide and its active metabolite, 5-(3-methyltriazeno)-imidazole-4-carboxamide (MTIC). Neutropenia and thrombocytopenia were dose limiting at 1000 mg/m2. Temozolomide was absorbed rapidly (mean time to maximum concentration 1.4 hrs) and eliminated, with average half-life and apparent oral systemic clearance values of 1.8 hours and 97 ml/minute/m2, respectively. Mean systemic exposure to MTIC was 3.7% of temozolomide. No objective responses were observed. The maximum tolerated dose of temozolomide was 750 mg/m2.

CONCLUSION

Temozolomide 750 mg/m2 administered orally every 28 days was well tolerated. Alternate temozolomide dosing schedules such as continuous daily administration may enhance antitumor activity through sustained depletion of the DNA repair protein O6-alkylguanine DNA alkyltransferase.

Pharmacology of anticancer drugs in the elderly population

Modifications to bodily functions and physiology are known to occur with age. These changes can have a considerable impact on the pharmacokinetic processes of absorption, distribution, metabolism and excretion and the pharmacodynamic properties of administered drugs. For many drugs with a high therapeutic index, this will be clinically unimportant, but for anticancer drugs, which usually have a low therapeutic index, these pharmacological changes can lead to dramatic consequences, such as excessive drug concentrations and unacceptable toxicity, or subtherapeutic drug concentrations and ineffective treatment. Despite the increased susceptibility of the elderly to these changes, doses are rarely adapted on the basis of pharmacokinetics and pharmacodynamics, with the exception of changes secondary to altered renal function. Until recently, only a few large prospective randomised trials have provided evidence-based data for dose adaptations in elderly patients. However, with increasing knowledge of the pharmacokinetics of anticancer drugs, advances in the knowledge of pharmacokinetic behaviour with aging, and documented efficacy and toxicity data in the elderly population, it is possible to highlight aspects of prescribing anticancer drugs in the elderly. In general, and for most drugs, age itself is not a contraindication to full-dose chemotherapy. The main limiting factors are comorbidity and poor functional status, which may be present in a significant number of the elderly population. Elderly patients with cancer are part of the daily practice of oncologists, but currently clinicians can often only estimate whether dose modification is advantageous for the elderly. This review attempts to elucidate the factors that can influence the pharmacokinetics of anticancer drugs frequently used in the elderly, and the clinical or biochemical parameters that form the basis for dose adjustments with age.

Pharmacological factors influencing anticancer drug selection in the elderly

Persons over the age of 65 years are the fastest growing segment of the US population. In the next 30 years this segment will represent more than 20% of the population. Fifty percent of all cancers occur in this age group and therefore the total cancer burden is expected to rise. Data are becoming available that will better guide the use of chemotherapy in the older patient population. Studies are presented discussing pharmacokinetic data on a number of chemotherapeutic agents with an emphasis on those that have entered clinical practice over the past few years. Many of these agents seem to have a beneficial therapeutic index, particularly in regard to older patients. Aging can affect the pharmacokinetics of chemotherapy in a number of ways. Absorption is only modified minimally by age. The greater concern with the use of oral drugs is patient compliance. Volume of distribution is affected by changes in body composition, anaemia and decreased plasma albumin concentration. There are many drugs in which renal excretion plays an important role. Decline in glomerular filtration is a consistent phenomenon with aging. Drug metabolism is primarily affected by changes in the P450 system and coadministration of drugs which also interact with this important enzyme system. The selection of chemotherapy in the elderly is frequently determined by degree of comorbidity and the patients' functional status. These factors are critical and can often determine response and toxicity. This article discusses the changes that occur with antimetabolites, camptothecins, anthracyclines, taxanes, platinum compounds, epipodophyllotoxins and vinca alkaloids. There has also been an increasing trend toward the use of oral chemotherapy. Factors that must be considered in selecting chemotherapeutic agents include limitations of saturability of absorption, patient compliance and the pharmacokinetic and pharmacodynamic changes that occur in older patients. Interpatient variability and age-related changes in drug metabolism are discussed. Careful attention to the physiological changes with age and dose adjustments necessary for end-organ dysfunction (renal, hepatic) are needed to ensure the safe administration of chemotherapy. In this article specific diseases are discussed (breast, colon, ovarian and non-small lung cancers) with recommendations for drug selection in adjuvant chemotherapy and the treatment of metastatic disease. Future studies will need to incorporate these various factors to properly evaluate chemotherapy in older patients. Research and educational initiatives targeted to this population will need to be a priority.

Pharmacology of antineoplastic agents in older cancer patients

Persons over the age of 65 years are the fastest growing segment of the United States population. In the next 30 years it will comprise over 20% of the population. Fifty percent of all cancers occur in this age group and therefore there will be an expected rise in the total cancer burden. Data is becoming available which will better guide the use of chemotherapy in the older patient population. Studies will be presented discussing pharmacokinetic data on a number of chemotherapeutic agents with an emphasis on those which have entered practice over the past few years. Many of these agents seem to have a beneficial therapeutic index, particularly in regard to older patients. There has also been an increasing trend toward the use of oral chemotherapy. Factors that must be considered in choosing chemotherapy include limitations of saturability of absorption, patient compliance and the pharmacokinetic and pharmacodynamic changes which occur in older patients. Interpatient variability and age related changes in drug metabolism are discussed. Careful attention to the physiologic changes with age, and dose adjustments necessary for end organ dysfunction (renal, hepatic) are needed to ensure the safe administration of chemotherapy.

Temozolomide in combination with interferon alpha-2b in patients with metastatic melanoma: a phase I dose-escalation study

BACKGROUND

Metastatic melanoma (MM) is associated with a high risk of central nervous system (CNS) metastases, and current chemotherapy does not adequately treat or protect patients with MM against CNS metastases. Therefore, the authors initiated a Phase I study to determine the pharmacokinetics and safety profile of temozolomide (TMZ), a novel oral alkylating agent known to cross the blood-brain barrier, in combination with interferon alpha-2b (IFN-alpha2b).

METHODS

Twenty-three patients with MM were enrolled in this single-center, open-label study. Patients with CNS metastasis were excluded. One cohort (n = 6 patients) received oral TMZ (200 mg/m(2) per day) for 5 days every 28-day cycle plus subcutaneous IFN-alpha2b (5 million International Units [MIU]/m(2) per day, 3 times per week). A second cohort (n = 17 patients) received TMZ 150 mg/m(2) per day on the same schedule plus escalating doses of IFN-alpha2b (5.0 MIU/m(2) per day, 7.5 MIU/m(2) per day, and 10 MIU/m(2) per day 3 times per week).

RESULTS

The most common adverse events were fatigue, fever, nausea/emesis, anxiety, and diarrhea. Most toxicity was mild to moderate in severity. The primary dose-limiting toxicity was thrombocytopenia. The maximum tolerated dose was either TMZ 150 mg/m(2) plus IFN-alpha2b 7.5 MIU/m(2) or TMZ 200 mg/m(2) plus IFN-alpha2b 5.0 MIU/m(2). Four patients (17%) had objective responses (one complete response and three partial responses), and four patients had stable disease. The median survival was 9 months. The pharmacokinetics of TMZ were not affected by coadministration of IFN-alpha2b.

CONCLUSIONS

TMZ can be combined safely with IFN-alpha2b. This regimen demonstrated clinical activity in patients with MM and merits further investigation to define its effect on the incidence of brain metastases.

Dosing strategies for anticancer drugs: the good, the bad and body-surface area

Most anticancer drugs are characterised by a narrow therapeutic window; hence, a small change in dose can lead to poor antitumour effects or an unacceptable degree of toxicity. The rationale for using body surface area (BSA) to dose antineoplastic agents is to normalise the effects of drugs, and accordingly, it has been routinely employed as the only independent variable. In the last 10 years, however, several studies have shown a poor relationship of BSA for predicting drug exposure, and an irrelevant correlation between this variable and pharmacokinetic (PK) parameters. In this paper, the results of this relationship for various commonly used antineoplastic agents are reviewed, and the influence of BSA to decrease the total variability in clearance among patients is underlined. As reported, BSA failed to individualise the effects of the majority of the agents explored. The criteria that can predict a clinically meaningful relationship between BSA and drug clearance are discussed, and some alternative strategies to dose agents when BSA has proven to be useless are proposed.

Pharmacokinetic considerations of oral chemotherapy in elderly patients with cancer

Persons over the age of 65 years are the fastest growing segment of the US population. In the next 30 years they will comprise over 20% of the population. Fifty per cent of all cancers occur in this age group and therefore there will be an expected rise in the total cancer burden. There has been an increasing trend over the past 20 years toward the use of oral chemotherapy. This change has been encouraged by the need to decrease the costs of chemotherapy administration, patient preferences and quality of life issues. Factors that must be considered with oral chemotherapy administration include limitations of saturability of absorption, patient compliance and pharmacokinetic/pharmacodynamic changes which occur in elderly patients. Interpatient variability and drug metabolism, particularly age-related changes in drug metabolism are being studied. The cytochrome P450 system has been intensively studied because of its importance with regard to chemotherapeutic drugs. This article reviews these issues and provides details regarding specific drugs including temozolomide, thalidomide, topotecan, the fluoropyrimidines, etoposide, hydroxycarbamide (hydroxyurea), tamoxifen, and alkylating drugs. Complementary and alternative therapies are also discussed.