Patterns of regional node irradiation therapy following breast-conserving surgery: Report from the National Cancer Data Base 2003-2007.

Abstract

1101 Background: A recent randomized trial (MA.20) showed that regional nodal irradiation (RNI) in addition to breast irradiation in high risk node negative and 1-3 node positive patients undergoing breast-conserving therapy (BCT) reduced the risk of recurrence and improved disease-free survival. We investigated the trends of RNI use in the United States and related factors for the use of RNI using the National Cancer Data Base. Methods: This study includes 292,598 stage I-III breast cancer patients without neoadjuvant therapy who underwent BCT from 2003-2007. We investigated pathological, patient, and facility factors related to RNI use, by multivariable logistic regression, with odds ratio (OR) estimations. Results: The proportion of radiotherapy use after BCT slightly declined from 78.6% in 2003 to 75.6% in 2007. The use of breast irradiation plus RNI decreased from 10.8% in 2003 to 8.3% in 2007 (p<0.0001). The number of tumor positive lymph nodes strongly determined the use of additional RNI: 4.4% patients with negative nodes, 22.8% patients with 1-3 nodes, and 39.7% patients with 4 or more nodes received breast irradiation plus RNI after undergoing BCT (p<0.0001). The proportion of patients undergoing RNI significantly decreased over the study period from 43.3% to 37.2% in the 4+ node positive group, and from 23.6% to 22.0% in the 1-3 node positive group. At comprehensive community cancer centers, 25.5% patients with 1-3 positive nodes were treated with breast irradiation plus RNI (vs. 23.2% in community cancer centers and 21.1% in academic/research cancer centers). Among node negative patients, 11.5% of those with tumor size greater than 5 cm received additional RNI, compared to 4.3% in patients with tumors less than 5cm (p<0.0001). Other significant factors related to RNI use included higher tumor grade, younger age, facility location, and facility volume. Conclusions: The use of RNI varies by number of tumor positive nodes and facility factors. Only 22.8% of patients with 1-3 positive nodes underwent RNI. Future studies are needed to determine if the use of RNI will increase after publication of the MA.20 trial especially for the 1-3 node positive group.