Re: Categorical covariates

Susan, What kind of dependent variable do you have in your model? If you are doing a PK analysis then my guess its probably not worth the effort to see if tumour type is a covariate unless you have lots and lots of patients with each tumour type (e.g. 100/tumour). A more informative covariate might be a performance score like ECOG which you might have in most patients without having to consider a wide spectrum of tumour types. If you are doing something more interesting like looking at tumour size and response to treatment then you may be able to pool the tumour types into groups based on biological origin and perhaps learn something about tumour growth. See Tham et al. 2008 for an example of a tumour growth model. Best wishes, Nick Tham LS, Wang L, Soo RA, Lee SC, Lee HS, Yong WP, et al. A pharmacodynamic model for the time course of tumor shrinkage by gemcitabine + carboplatin in non-small cell lung cancer patients. Clin Cancer Res. 2008;14(13):4213-8. Hudachek,Susan wrote: > Greetings All! Does anyone have any suggestions on how to add in cancer type > (roughly 10 different tumor types) as a covariate? Thanks for any and all input! > Susan > > Susan Hudachek, M.S., Ph.D. > Animal Cancer Center > Veterinary Teaching Hospital > Colorado State University > 300 West Drake Road > Fort Collins, CO 80523-1620 > PHONE: (970) 219-7599 > FAX: (970) 297-1254 > EMAIL: [EMAIL PROTECTED] -- Nick Holford, Dept Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand [EMAIL PROTECTED] tel:+64(9)373-7599x86730 fax:+64(9)373-7090 http://www.fmhs.auckland.ac.nz/sms/pharmacology/holford