SQL Server 2012 :: Pattern Matching And Data Conversion

I have a table ("MyData") with string columns that have nvarchar data that looks like this:

ColA
--------
42/90
78/109

I plan to do a mathematical grouping on the numerator (eg: 0-10,11-20,21-30, etc... ), So I need to grab the numerator and turn it into an int. For reasons I can't get into, I have to do this in pure T-SQL.

So my question: How would I write a select statement that regex pattern matches "^([0-9]+)/" on ColA and returns integers instead of text?

E.g. THis Query:

SELECT [magic t-sql syntax] as Converted_ColA from MyData

should return this set of int values:

42
78