For patients who are incidentally found to have pT1a invasive breast cancer on excision for presumed atypia/DCIS without a sentinel lymph node biopsy, will you irradiate without the SLNB being performed?  

Unless systemic treatment would change, I would not push for SNLN as the yield of SNLN for low volume IDC has to be weighed against the small but not insignificant risk of lymphedema and other side effects. When treating with whole breast, would include level 1 and 2 in RT field. In the era of syst...

All those factors you listed are important. Is this a microinvasive cancer (i.e., few cells up to 2 mm), triple negative or ER/PR positive, age higher or lower? No LVI? How big was the DCIS component? How high was the DCIS grade (presume that atypia/DCIS issue was lower grade)? If this is a tiny inv...