st: Survival analysis - comparing a subset of the sample to the entiresample

[Richard Aplenc <raplenc@cceb.med.upenn.edu>]

Hi,

I have a dataset with 1200 patients and time to event (relapse and
death).  Of these patients, 500 have data on a particular genotype, of 
which the variant allele is associated with an increased relapse risk.

I would like to compare the relapse free survival estimate (RFS) of the
overall study group to the RFS estimate of the patients with genotypes. 
 That is, I want to show that the patients with genotype information 
(both wildtype and variant genotypes combined) do not overall have a 
significantly different risk of relapse than all patients on the trial.

Thus, I have 2 questions:

1. How do I do this in STATA?

2. Are there issues of lack of independance in the data that make this 
comparison problematic from a statistical standpoint?

Thank you very much in advance.

Richard
--
Richard Aplenc, MD, MSCE
Pediatric Oncology/Stem Cell Transplant
Children's Hospital of Philadelphia
Center for Clinical Epidemiology and Biostatistics
University of Pennsylvania
215-573-0259 (lab)
215-590-4183 (fax)
raplenc@cceb.med.upenn.edu

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