@aj456 - I am sure there are members who've not gone down the Radiation route .... no doubt you'll hear from some soon.
I had the choice of NOT doing radiation (on a trial) - but I chose to go ahead with it, as I figured the Rads would mop up any random cells that the surgeon may have missed. 6.5 years later, so far, so good.
To be honest, the last thing you want, would be a recurrence - 'specially if you'd bypassed the recommended treatment advice. The 'what ifs' would muck with your brain if you don't do the Rads & then further down the line, have a recurrence.
There is always the chance of a recurrence ANYWAY - but if you don't throw the kitchen sink at it ... you'd always be wondering ....
High Grade 'anything' is not always a good diagnosis - and your team is recommending the best treatment for YOUR best results (ie hopefully no recurrence.)
Maybe ask your Rad Onc if THEY would have the treatment if it was 'their' diagnosis .... or if it was their sister or mother - would they encourage them to have it. Radiation usually has less side effects of ANY of the treatments for BC ... so try not to be scared of it xx
take care & all the best with your decision making.