Can I cancel my UK Visa and re-apply for it later?

I have my Tier 5 (Youth Mob) visa already stamped in my passport and ready to go for the 15th of September, however I am traveling around the USA on my way there and currently I am thinking of staying for up to 6 months in the US - which will obviously mean that I won't be in the UK on my visa start date.
I am hoping to cancel my Youth Mobility Visa and come back to my home country and re-apply for it once I have come back from my USA trip. Is it possible to do this?
I have a friend who lost her passport before arriving to the UK so called up and got her visa cancelled, so its my understanding that this should be fine.

Just wanted to double check!

Thanks

Hey,

Did you end up cancelling your Youth Mobility visa? I'm in a similar situation