Remove digits from a field value

I am trying to remove the digits from a field value ie, CT20170228-0044 using

set mystring [lindex $xlateInVals 0]

regexp {[A-Za-z]+$} $mystring field16

set xlateOutVals

knowing the dash may be the culprit I have split the value and used the command on just the first component CT20170228. I have scoured Clovertech for resolution and tried different iterations of the command.

using TCL

regexp