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The impact of non-drug-related toxicities on the estimation of the maximum tolerated dose in phase I trials.

ABSTRACT: The rate of observed dose-limiting toxicities (DLT) determines the maximum tolerated dose (MTD) in phase I trials. There are cases in which non-drug-related toxicities or other-cause toxicities (OCT) are flagged as DLTs, or vice versa, due to attribution errors. We aim to assess the impact of such errors on the final estimate of MTD. We compared the impact of attribution errors using 2 trial designs-the "3+3" dose-escalation scheme and the continual reassessment method (CRM). Two attribution errors are considered: when a DLT is classified as an OCT (type A error) and when an OCT is misclassified as a DLT (type B error). The impact of these errors on accuracy, patient safety, sample size, and study duration was evaluated by varying the probability of occurrence of each error through simulated trials. Under no errors, CRM is on average 35% more accurate than 3+3 in finding the true MTD. This improved accuracy is maintained in the presence of errors. At a 15% type B error rate, CRM recommends a dose within 2 levels of the true MTD 68% of the time, compared with 17% of the time using the 3+3 method. A DLT must be attributed as an OCT 30% of the time to increase the accuracy of 3+3; otherwise the method recommends a wrong dose approximately 75% of the time. CRM is more robust to toxicity attribution errors compared with the 3+3 as it uses information from all treated patients, leading to a more accurate MTD estimation at the frequency of attribution errors anticipated in phase I clinical trials.

SUBMITTER: Iasonos A

PROVIDER: S-EPMC3463734 | biostudies-literature | 2012 Oct

REPOSITORIES: biostudies-literature

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The impact of non-drug-related toxicities on the estimation of the maximum tolerated dose in phase I trials.

Iasonos Alexia A Gounder Mrinal M Spriggs David R DR Gerecitano John F JF Hyman David M DM Zohar Sarah S O'Quigley John J

Clinical cancer research : an official journal of the American Association for Cancer Research 20120723 19

The rate of observed dose-limiting toxicities (DLT) determines the maximum tolerated dose (MTD) in phase I trials. There are cases in which non-drug-related toxicities or other-cause toxicities (OCT) are flagged as DLTs, or vice versa, due to attribution errors. We aim to assess the impact of such errors on the final estimate of MTD. We compared the impact of attribution errors using 2 trial designs-the "3+3" dose-escalation scheme and the continual reassessment method (CRM). Two attribution err ...[more]

PMID: 22825582

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Project description:Background. Absent adaptive, individualized dose-finding in early-phase oncology trials, subsequent 'confirmatory' Phase III trials risk suboptimal dosing, with resulting loss of statistical power and reduced probability of technical success for the investigational therapy. While progress has been made toward explicitly adaptive dose-finding and quantitative modeling of dose-response relationships, most such work continues to be organized around a concept of 'the' maximum tolerated dose (MTD). The purpose of this paper is to demonstrate concretely how the aim of early-phase trials might be conceived, not as 'dose-finding', but as dose titration algorithm (DTA)-finding. Methods. A Phase I dosing study is simulated, for a notional cytotoxic chemotherapy drug, with neutropenia constituting the critical dose-limiting toxicity. The drug's population pharmacokinetics and myelosuppression dynamics are simulated using published parameter estimates for docetaxel. The amenability of this model to linearization is explored empirically. The properties of a simple DTA targeting neutrophil nadir of 500 cells/mm 3 using a Newton-Raphson heuristic are explored through simulation in 25 simulated study subjects. Results. Individual-level myelosuppression dynamics in the simulation model approximately linearize under simple transformations of neutrophil concentration and drug dose. The simulated dose titration exhibits largely satisfactory convergence, with great variance in individualized optimal dosing. Some titration courses exhibit overshooting. Conclusions. The large inter-individual variability in simulated optimal dosing underscores the need to replace 'the' MTD with an individualized concept of MTD i . To illustrate this principle, the simplest possible DTA capable of realizing such a concept is demonstrated. Qualitative phenomena observed in this demonstration support discussion of the notion of tuning such algorithms. Although here illustrated specifically in relation to cytotoxic chemotherapy, the DTAT principle appears similarly applicable to Phase I studies of cancer immunotherapy and molecularly targeted agents.

Project description:BackgroundTargeted agents, such as antiangiogenic drugs (e.g., bevacizumab) and poly(ADP-ribose) polymerase inhibitors (e.g., rucaparib), have been shown to improve outcomes in patients with newly diagnosed or recurrent ovarian cancer. Evidence suggests that combinations of these two classes of targeted agents may result in synergistic antitumor activity.ObjectiveThe phase I portion of MITO 25 was designed to determine the maximum tolerated dose, pharmacokinetics, and the safety profile of rucaparib when administered in combination with bevacizumab as maintenance treatment for patients with high-grade epithelial ovarian, fallopian tube, or primary peritoneal cancer.MethodsThis was a single-arm, phase I dose-escalation study. Cohorts of three patients were recruited to receive increasing rucaparib doses of 400 mg, 500 mg, or 600 mg twice daily for 28 days. Bevacizumab 15 mg/kg was administered at day 1 every 21 days.ResultsWe enrolled nine patients. Two patients in the rucaparib 600-mg group had four grade 3 treatment-emergent adverse events: increased in alanine aminotransferase and aspartate aminotransferase levels, depression, and hallucinations. These were deemed to be dose-limiting toxicities related to rucaparib. Because these dose-limiting toxicities occurred in the 600-mg group and affected more than one in three patients, the maximum tolerated dose for rucaparib was considered 500 mg twice daily when combined with bevacizumab 15 mg/kg at day 1 every 21 days. There were no new safety concerns from using the combination. No substantial difference in pharmacokinetic parameters was found between the cohorts or in the pharmacokinetic profiles of rucaparib administered alone or with bevacizumab with respect to historical controls.ConclusionsThe maximum tolerated dose of rucaparib is 500 mg twice daily when co-administered with bevacizumab. The plasma concentration-time profiles of rucaparib in combination with bevacizumab suggest no pharmacokinetic interactions between the drugs. The randomized phase II portion of MITO 25 will further investigate rucaparib maintenance treatment with or without bevacizumab in patients with newly diagnosed stage III-IV ovarian cancer who responded to carboplatin-paclitaxel chemotherapy with or without bevacizumab.Trial registrationClinicalTrials.gov identifier NCT03462212; registered March 2018.

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The impact of non-drug-related toxicities on the estimation of the maximum tolerated dose in phase I trials.

Publications

The impact of non-drug-related toxicities on the estimation of the maximum tolerated dose in phase I trials.

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