What is the role for RNI in a postmenopausal female with clinically N+, hormone receptor positive breast cancer s/p lumpectomy and ALND with low volume nodal disease (e.g., 1/12 nodes positive)?

When thinking about low volume nodal disease in cN+ patients, I tend to think about MA20 which included patients undergoing an ALND and 85% had 1-3 LN involved. I will offer these patients adjuvant RT to the breast and RNI (SCV/axilla with consideration of IM nodes based on dosimetry) based on the improvement in locoregional recurrences, distant DFS, balanced against a relatively low toxicity rate at 10 years with RNI. Postmenopausal, hormone positive patients may have a lower benefit than higher risk cohorts but I would still have a discussion with patient regarding whole breast + RNI.

Whether a patient is clinically node negative or node positive is sometimes more related to the extent of the workup performed, rather than inherent differences in biology/prognosis. For instance, a women who has a breast MRI which picks up a small level I axillary LN that is subsequently biopsied (and is therefore considered cN+), may not be so different than some of the Z11/AMAROS patients who were considered cN0. This is of course different from a scenario of someone presenting with matted, bulky, or symptomatic axillary nodes (cN2). Thus, I think applying similar principals to the low-volume cN1 pN1a population as are applied to the cN0 pN1a population is reasonable.

In my practice, I generally weigh the additional patient/disease facto...

I think @Dr. First Last and @Dr. First Last are a little too reticent in their recommendation for RNI in a patient with 1 positive axillary node. In addition to the data cited from MA-20 one should consider all the PMRT data which has convincingly demonstrated the value of RT for pts with 1-3 pos axillary nodes. (Marks LB, Zeng J, Prosnitz LR.One to three versus four or more positive nodes and postmastectomy radiotherapy: time to end the debate. J Clin Oncol. 26(13):2075-7, 2008.) See this old editorial for additional references. I thought we had settled this one a while back.

That value seems greater incidentally than might be expected from a consideration of local recurrence data and has specifically been noted for pts with 1 pos node in...