How do I run the sed command with input and output as the same file?

I'm trying to do use the sed command in a shell script where I want to remove lines that read STARTremoveThisComment and lines that read removeThisCommentEND.

I'm able to do it when I copy it to a new file using

sed 's/STARTremoveThisComment//' > test

But how do I do this by using the same file as input and output?