afatinib / cetuximab dosage question - 1265574

Sun, 08/24/2014 - 16:55

In recent news articles about positive results from a trial of 126 people on the afatinib / cetuximab combination, they state the dosage was: afatinib (40 mg oral daily) plus cetuximab (500 mg/m2 intravenously every 2 weeks). http://www.onclive.com/web-exclusives/Promising-Findings-for-AfatinibCe…

I'm on a different dosage for the cetuximab (250 mg/m2 intravenously once a week). The afatinib is the same.

If the news articles hadn't recently been published, I would not have any reference on dosage. But now that I do, I can't get the different dosing schedule off my mind. There is a new trial underway testing a weekly dose. https://clinicaltrials.gov/ct2/show/NCT02020577?term=afatinib+cetuximab… So perhaps that is where the different dosage is originating.

Is this weekly, lower dose just as common? Thoughts?

Thanks, RM

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JimC

Hi RM,

It's been used at both dosages, and of course the total dose over a two week period is identical. Often, proportionately smaller dosages of drugs are given weekly in order to minimize side effects, and cetuximab can have significant toxicity for some patients, especially in combination with another drug such as afatinib.

Also, the half-life of cetuximab is almost five days, so at the time of the subsequent infusion there is a significant amount of the drug in your system left over from the previous dose. I haven't found a study directly comparing the two dosing schedules in terms of efficacy, but if the weekly regimen reduces side effects and allows you to continue treatment, that is always a positive factor - a possibly more effective dosing schedule doesn't help you if you have have to quit because of toxicity issues.

JimC
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Dr West

The weekly dosing is far more common, and there is no reason to think that it is less effective than the every other week schedule, which I believe was tried as an attempt to mimimize the practical burden of IV cetuximab given as the only IV medication in a regimen we'd hope to administer for a long time.

To my knowledge, there has beeen no other work on this regimen presented since this published paper was first reported at live meetings several years ago.

Good luck.

-Dr.West