Abstract P1-10-12: Radiation therapy in 1-3 node positive mastectomy patients: Who benefits?
Authors: Ellis ED , Scanlan JM , Kaplan HG , Kieper DA , Morris AD , Atwood M 
Published: March 2017

Abstract
Introduction A recent meta-analysis on radiation therapy (XRT) demonstrated improved outcomes and recommended its use. However, these data were derived from the 1960's-1980's and might not reflect the effects of XRT when used in modern oncology practice [1]. Consequentially, XRT benefits for mastectomy patients with 1–3 positive nodes at the time of surgery (SX) remain uncertain. In this retrospective study we examined XRT effects in a modern cohort of mastectomy patients with 1–3 positive nodes at SX, across multiple outcomes: loco-regional recurrence (LRR), distant recurrence (DR), total recurrence (TR), breast cancer (BCa mortality) and all-cause mortality (ACM).
Subjects The Swedish Cancer Institute's breast cancer patient registry was used to identify mastectomy patients who had 1-3 positive lymph nodes at SX and known HER-2 receptor status. HER-2 positive patients who did not receive Herceptin were excluded.
Methods Clinical, pathological, treatment and outcomes data were extracted from our registry. Logistic multiple regressions were used to identify clinical and pathology elements available at the time of SX that correlated with LRR, DR, TR, BCaM and ACM. Regression model elements included: tumor receptor status - estrogen (ER), progesterone (PR) and HER-2, presence or absence of lymphovascular invasion (LVI), extension of LVI, number of LN+, node positivity ratio (positive/examined), surgical margins (SxM); patient age, chemotherapy, XRT and hormonal treatment.
Results The application of these filters to our breast cancer registry yielded 935 patients with a mean follow up time of 7 years. Our sample was “modern”: 95% of our patients were diagnosed after 1999, 80% after 2004. Logistic regression indicated that across all patients, XRT was associated with improved LRR (Nagelkerke R2=5%, p&lt;.01), and ACM (Nagelkerke R2=1%, p&lt;.05). The four clinical and pathologic elements that most strongly correlated with outcomes were LVI (+), LN+&gt;1, PR (-) and SxM (+) and we stratified the population into risk groups based on the number of factors present; low-risk = no factors, medium-risk = 1 factor, High-risk = 2+ factors. We also stratified by treatments, comparing the effects of chemotherapy alone vs. chemotherapy plus XRT across the major patient outcomes and risk groups (see Table 1). This comparison only showed XRT effects for LRR in the higher risk groups.
XRT effects by Risk Groups TREATMENTN=LRRDRTRBCa Mort.ACMLow RiskCH+, No XRT1080%4.6%4.6%2.9%3.7%GroupCH+, XRT+410%2.5%2.5%2.4%2.5%Medium RiskCH+, No XRT2152.8%10.2%12.1%5.6%10.7%GroupCH+, XRT+1880% *8.5%8.5%4.3%6.4%Highest RiskCH+, No XRT834.8%8.4%13.3%8.4%16.9%GroupCH+, XRT+122.8% +13.1%13.9%8.2%13.1%* =p&lt;.05, + =p&lt;.07
Discussion XRT improved LRR in the medium and high risk groups, but lacked benefit in the low-risk group and did not provide statistically significant improvements in BCa survival. These results suggest caution in using XRT in low-risk patients, but it has some value in reducing LRR in medium and high-risk populations, without survival benefits.
1. Lancet Volume 383, No. 9935, p2127–2135, 21 June 2014.
Citation Format: Ellis ED, Scanlan JM, Kaplan HG, Kieper DA, Morris AD, Atwood M. Radiation therapy in 1-3 node positive mastectomy patients: Who benefits? [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-10-12.