@elliej: Atypical ductal hyperplasia (see below) is not cancer yet so that may be why radiation doesn't affect it. Your Oncotype score was 16 but your risk of recurrence was 4%? Assuming this was with tamoxifen. That seems low for a score of 16 but there may be mitigating factors so that is an encouraging number. From googling:

Atypical ductal hyperplasia is a histologically borderline lesion that has some, but not all, of the features of ductal carcinoma in situ. Sometimes the distinction between Atypical ductal hyperplasia and ductal carcinoma in situ are simply defined on the number of ducts involved.
Pathology
Atypical ductal hyperplasia is a lesion with malignant potential. It lacks the strict criteria for ductal carcinoma in situ, with <2 ducts involved 3.

I think we all need to be careful in comparing our cases. @callalloo had DCIS (invasive), you have invasive ductal grade 1, I had invasive mixed ductal and lobular grade 3. All I can say is that if you feel trust on your doctor, move forward. If you don't, then get another opinion(s).

It sounds like you are ready to roll with radiation. Since you had a lumpectomy, that seems reasonable and your doc suggested it (though you have a choice of course). I really hope you give hormonal meds a good chance. Side effects change and ease up over time, in my experience, if not others'. I am around your age and get it!