Designs of drug-combination phase I trials in oncology: a systematic review of the literature.

BACKGROUND: Combining several anticancer agents can increase the overall antitumor action, but at the same time, it can also increase the overall observed toxicity. Adaptive dose-escalation designs for drug combinations have recently emerged as an attractive alternative to algorithm-based designs, and they seem more effective in combination recommendations. These methods are not used in practice currently. Our aim is to describe international scientific practices in the setting of phase I drug combinations in oncology. MATERIAL AND METHODS: A bibliometric study on phase I dose-finding combination trials was conducted using the Medline(®) PubMed database between 1 January, 2011, and 31 December 2013. Sorting by abstract, we selected all papers involving a minimum of two agents and then retained only those in which at least two agents were dose-escalated. RESULTS: Among the 847 references retrieved, 162 papers reported drug-combination phase I trials in which at least two agents were dose-escalated. In 88% of trials, a traditional or modified 3 + 3 dose-escalation design was used. All except one trial used a design developed for single-agent evaluation. Our study suggests that drug-combination phase I trials in oncology are very safe, as revealed by the calculated median dose-limiting toxicity rate of 6% at the recommended dose, which is far below the target rate in these trials (33%). We also examined requirements of phase I clinical trials in oncology with drug combinations and the potential advantages of novel approaches in early phases. CONCLUSION: Efforts to promote novel and innovative approaches among statisticians and clinicians appear valuable. Adaptive designs have an important role to play in early phase development.

Competing designs for drug combination in phase I dose-finding clinical trials.

The aim of phase I combination dose-finding studies in oncology is to estimate one or several maximum tolerated doses (MTDs) from a set of available dose levels of two or more agents. Combining several agents can indeed increase the overall anti-tumor action but at the same time also increase the toxicity. It is, however, unreasonable to assume the same dose-toxicity relationship for the combination as for the simple addition of each single agent because of a potential antagonist or synergistic effect. Therefore, using single-agent dose-finding methods for combination therapies is not appropriate. In recent years, several authors have proposed novel dose-finding designs for combination studies, which use either algorithm-based or model-based methods. The aim of our work was to compare, via a simulation study, six dose-finding methods for combinations proposed in recent years. We chose eight scenarios that differ in terms of the number and location of the true MTD(s) in the combination space. We then compared the performance of each design in terms of correct combination selection, patient allocation, and mean number of observed toxicities during the trials. Our results showed that the model-based methods performed better than the algorithm-based ones. However, none of the compared model-based designs gave consistently better results than the others.

Cephalometric assessment of craniofacial dysmorphologies in relation with Msx2 mutations in mouse.

OBJECTIVES: To determine the role of Msx2 in craniofacial morphology and growth, we used a mouse model and performed a quantitative morphological characterization of the Msx2 (-/-) and the Msx2 (+/-) phenotype using a 2D cephalometric analysis applied on micrographs. MATERIALS AND METHODS: Forty-four three-and-a-half-month-old female CD1 mice were divided into the following three groups: Msx2 (+/+) (n = 16), Msx2 (+/-) (n = 16), and Msx2 (-/-) (n = 12). Profile radiographs were scanned. Modified cephalometric analysis was performed to compare the three groups. RESULTS: Compared with the wild-type mice, the Msx2 (-/-) mutant mice presented an overall craniofacial size decrease and modifications of the shape of the different parts of the craniofacial skeleton, namely the neurocranium, the viscerocranium, the mandible, and the teeth. In particular, dysmorphologies were seen in the cochlear apparatus and the teeth (taurodontism, reduced incisor curvature). Finally contrary to previous published results, we were able to record a specific phenotype of the Msx2 (+/-) mice with this methodology. This Msx2 (+/-) mouse phenotype was not intermediate between the Msx2 (-/-) and the wild-type animals. CONCLUSION: Msx2 plays an important role in craniofacial morphogenesis and growth because almost all craniofacial structures were affected in the Msx2(-/-) mice including both intramembranous and endochondral bones, the cochlear apparatus, and the teeth. In addition, Msx2 haploinsufficiency involves a specific phenotype with subtle craniofacial structures modifications compared with human mutations.