do i need radiotherapy on the axillary lymph nodes?

I am 49 ys old, I was diagnosed to have less than 5mm invasive ductal carcinoma gradeII. Lumpectomy was done. it was positive for estrogen and progesterone. Negative for her2 and ki67. Dynamic MRI on the breast was free. MRI on the axilla was free. CEA and CA 15.3 were negative. I started conformal radiotherapy on the brast only without axillary LNs. I want to ask if there is any non-invasive way to cofim that the lymh nodes are free?  Do I have to hvae prophylactic radiotherapy on the axilla? What about lymphdema? I really need advice. Thanks alot for your help.
N.B lumpectomy was done for excision of ductectesia that caused bleeding from left nipple, mamogram (mammogram) and ultrasound reveade only ductectasia with no mass detected.