Practical implementation of a modified continual reassessment method for dose-finding trials.
OBJECTIVE
We describe a practical, reliable, efficient dose-finding design for cytotoxic drugs applied in a multi-institutional setting.


METHODS
The continual reassessment method (CRM) was modified for use in phase I trials conducted through the New Approaches to Brain Tumor Therapy (NABTT) Consortium. Our implementation of the CRM uses (1) a simple dose-toxicity model to guide data interpolation, (2) groups of three patients to minimize calculations and stabilize estimates, (3) investigators' clinical knowledge or opinion in the form of data to make the process easier to understand, and (4) a flexible computer program and interface to facilitate calculations.


RESULTS
The modified CRM was used in two dose-finding trials of 9-aminocamptothecin in patients with newly diagnosed and recurrent glioblastoma who were taking anticonvulsant medication. The CRM located the maximum tolerated dose (MTD) efficiently in both trials. Compared to conventional designs, the CRM required slightly more than half the number of patients expected, did not greatly overshoot the MTD (i.e. no patients were treated at dangerously high doses), and did not underestimate the MTD.


CONCLUSIONS
Our experience demonstrates the feasibility of implementing this design in multi-institutional trials and the possibility of performing dose-finding studies that require fewer patients than conventional methods.
Piantadosi
S
S
Johns Hopkins Oncology Center, Baltimore, Maryland, USA.
Fisher
J D
JD
Grossman
S
S
D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000009:adverse effects; D001932:Brain Neoplasms / Q000188:drug therapy*; D002166:Camptothecin / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives*; D017321:Clinical Trials, Phase I as Topic; D004305:Dose-Response Relationship, Drug; D005909:Glioblastoma / Q000188:drug therapy*; D006801:Humans; D008962:Models, Theoretical; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy*; D015203:Reproducibility of Results
D000970:Antineoplastic Agents; C080125:9-aminocamptothecin; D002166:Camptothecin