Given the new ASCO guidelines on SNB in early stage breast cancer, how does the omission of SNB in patients aged 50-70 impact your adjuvant radiation recommendations?

If the patient is otherwise a good candidate for APBI (age > 50, pT1 tumor, ER+, HER2 negative, Recurrence score low and intending to take endocrine therapy) that was clinically node negative and ultrasound axilla negative, I feel completely comfortable treating with APBI post lumpectomy with negative margins in the absence of a SN biopsy. The SN biopsy is a diagnostic test that does not treat the axilla, and the endocrine therapy treats the risk associated with the small likelihood of meaningfully positive nodes (~5% macromets, ~8% micromets on the SOUND trial).

Based on the EBCTCG RNI meta-analysis, DBCG, and MA.20, I would consider RNI in patients with central or medial tumors or those with T2 grade 3 disease.

However, I've encouraged our surgeons to continue SLND, at least in patients aged 50-70.

What should the primary outcomes be in INSEMA and SOUND? Is SLNB a treatment or a diagnostic tool? Do we need a study to determine if there is an OS benefit to a PET scan?

The rationale behind the study, for some, is that Oncotype determines whether chemo is indicated, not node-positive disease. If this is the only concern, then there is already an answer, and we have the RxPONDER trial. For rad onc, however, the main issue with INSEMA and SOUND revolves around whether one believes there is a benefit wi...

Reading these comments—and seeing it in practice—I think there is a tendency to overgeneralize the SOUND and INSEMA trials, applying them to patients who were not adequately represented in either study.

The NCCN 2026 guidelines state: "Based on SOUND and INSEMA trials, patients >50 years and postmenopausal with cT1N0 (node negative by axillary ultrasound), with HR+/HER2-negative, grade 1–2 tumors who are agreeable to receiving whole breast RT and endocrine therapy may be considered for omission of SLNB. Caution should be used in those with lobular histology."

Two points deserve emphasis:

First, on radiotherapy: in the SOUND no-axillary-surgery arm, only 10.8% received partial breast radiotherapy, and the INSEMA trial did not allow partial brea...