Credit: Original article published here.
Researchers of a study, published in Radiotherapy and Oncology, evaluated the effects of post-mastectomy radiation therapy in patients with HER-2 positive breast cancer based on pathological response to previous primary systemic therapy. The analyses used pooled data from the TRYPHAENA and NeoSphere randomized phase 2 trials.
According to the study’s lead author, Omran Saifi, patients who achieved a complete nodal pathological response (ypN0) after primary systemic therapy had “excellent locoregional-control” that supported deescalation of post-mastectomy radiation therapy. Conversely, patients with ypN2-3 disease showed significant benefits with radiation therapy.
Post-Mastectomy Radiotherapy Effect Per Nodal Status
The analyses included 312 pooled patients with node-positive disease who were treated with HER-2-targeted primary systemic therapies, followed by mastectomy with or without subsequent radiation therapy. The primary end point was loco-regional recurrence-free survival (LRRFS).
Researchers noted 172 (55%) patients achieved ypN0 response and 140 (45%) patients did not. Patients with ypN0 both with or without post-mastectomy radiation therapy had a 5-year LRRFS of 97% (P=.17). Patients with ypN1 disease (n=62) who received post-mastectomy radiation therapy (n=40) had a 5-year LRRFS of 89% compared with a LRRFS of 89% in those who did not receive radiation therapy (n=22; P=.60).
In addition, authors found a significant difference in LRRFS between the ypN2-3 (n=78) disease patients with post-mastectomy radiation therapy (n=53; 5-year LRRFS, 92%) compared with those who did not (n=25; 5-year LRRFS, 75%; P=.019). Lastly, loco-regional recurrence was significantly associated with nodal disease at diagnosis and complete pathological response.
Ultimately, Saifi and colleagues suggested that post-mastectomy radiation therapy was significantly beneficial in patients with ypN2-3 disease stage HER-2 positive breast cancer who received a primary systemic therapy and mastectomy.
Related: Cardiac Safety of Trastuzumab in HER2-Positive Breast Cancer
