Assessment of Radiation Trends in a Prospective Registry of Node Positive Patients With Triple Negative Breast Cancer

Abstract

Our center is a mixed academic and community based practice, leading to significant variations in chemotherapy and radiation regimens. We sought to assess practice patterns for treatment of node positive triple negative breast cancer at our institution, utilizing a prospective registry. We were especially interested in the impact of the MA.20 trial (Whelan et al., NEJM, 2015) on practice patterns, as this trial has limited our interest in enrolling these patients on current national dose de-escalation trials, such as RTOG 1304. Stage I-IV triple negative breast cancer patients were enrolled on a prospective registry at academic and community practices within our institution over the past 7 years. Patients with non-metastatic breast cancer, with a biopsy proven positive node at diagnosis or at the time of surgery, were included for analysis. Data was collected on stage, surgery type, and timing of chemotherapy. Radiation plans were reviewed in detail, with information gathered on dose per fraction, total dose, use of boost, contouring of regional nodes, and dose to regional nodes. Statistical analysis was performed in SPSS version 24. Information regarding radiation treatment was available for 96 patients with node positive, triple negative breast cancer. All of the 22 patients undergoing lumpectomy received radiation. Only 75% of patients undergoing mastectomy received post-mastectomy radiation (PMRT). All clinical stage T3 or T4 patients received PMRT, as compared to 66% of T1 patients and 58% of T2 patients. There was no difference in 4 year survival for mastectomy versus lumpectomy (76.5% vs 78.9%). PMRT use was higher for patients receiving neoadjuvant chemotherapy, 79% versus 65%, but this was not statistically significant (p=0.19). There was significantly higher use of PMRT after publication of the MA.20 trial, (71% vs 100%, p=0.05). Similarly, use of regional nodal radiation for patients undergoing lumpectomy increased from 69% to 100% for this same time period, though this was not statistically significant. Reviewing individual plans, elective radiation to the internal mammary nodes (IMN) increased from 61% pre MA.20 to 74% afterwards. Recurrence rates for patients with IMN radiation were 20% vs 33% in patients without directed IMN radiation, however, this trend was not statistically significant. Publication of the MA.20 trial impacted radiation practice at our institution. With small patient numbers, significant reductions in recurrence were not evident. Further analysis and collaboration with other institutions is encouraged to further explore the impact of regional nodal radiation on patient outcomes for node positive, triple negative breast cancer.