well, possible, yes. But depending on the pattern it may be little or a lot of work. The answer is not just simple.
Can you post a link to the pattern? Or can you provide a picture (maybe scanned) at least? That would help to evaluate the amount of change that needs to be done - or maybe someone knows a pattern just like it, or anything.
If your pattern can be found on libraries like Ravelry, maybe someone has made it in a different size before?