Studies demonstrate safety of omitting axillary nodal dissection for early-stage breast cancer with positive sentinel lymph node (+SLN) biopsy, although trial designs differed in radiation therapy (RT) fields. Regional nodal irradiation was separately shown to improve outcomes in high-risk patients. This led to lack of consensus in RT volumes. Clinical pathways (CPs) standardize care where practice varies unnecessarily. We evaluated the impact of changes to a CP guiding postoperative RT in women with +SLNs on practice patterns throughout a network.

We implemented a CP for management of breast cancer with postoperative RT designed to promote uniform nodal treatment. The CP recommended modified tangents (MTs) including level I/II nodes for women with micrometastases (pN1mi). For women with macrometastases (pN1a), CPs recommended including level I/II LN in MT and a third supraclavicular node (SCN) LN ± internal mammary nodes for women with adverse factors present.

RT fields of 233 women undergoing breast-conserving surgery with +SLN but not axillary nodal dissection were retrospectively reviewed: 25% had pN1mi disease and 75% pN1a. Of 127 women treated before CP changes, 35% with pN1mi and 22% with pN1a were treated with whole-breast irradiation alone. Following CP changes, 106 women were treated: 5% with whole-breast irradiation alone, 58% with MT, and 38% with MT + SCN field. Utilization of MT was associated with CP changes. Utilization of a third SCN field was associated with CP changes, pN stage, extracapsular extension, and total number of adverse factors.

CPs translate published data and institutional experience into management plans that promote evidence-based care and eliminate unnecessary practice variations. Recognizing that postoperative RT treatment volumes were heterogeneous, we modified the CP based upon the latest evidence for regional nodal irradiation, after which we found increased compliance and consistency with quality guidelines, which will also aid in tracking outcomes in future investigations.