Modeling And Validation Of A Nomogram To Predict N2 Or N3 Disease In Breast Cancer Patients With One To Three Sentinel Lymph Nodes

According to the results of ACOSOG Z0011 and AMAROS trials, excellent axillary regional control has been achieved for selected breast cancer patients with positive sentinel lymph node (SLN) who didn’t receive axillary dissection. However, no consensus has been reached regarding to the radiation fields. We developed a nomogram to predict N2 or N3 disease in which regional nodal irradiation is indicated for breast cancer patients. 1023 patients who were treated between 2002 and 2017 and met the following criteria were retrospectively analyzed: female patients initially diagnosed with invasive breast cancer, cN0, without neoadjuvant chemotherapy, underwent lumpectomy or mastectomy plus sentinel node biopsy followed by axillary dissection, and pathologically confirmed 1-3 positive SLN. N2 or N3 disease was defined as the total number of positive axillary nodes exceeding three in the final pathological report. Patients were divided into training group and validation group according to the date of surgery. Risk factors of N2 or N3 disease were analyzed and used to create a nomogram in 689 patients in the training group, and the nomogram was validated in 334 patients in the validation group. Of the 1023 patients included, the median age was 48 years (21-86), 458 (44.8%) underwent breast conserving surgery, and 155 (15.2%) had N2 or N3 disease. Multivariate stepwise logistic regression showed the number of positive SLN (p<0.001), the number of negative SLN (p<0.001), molecular subtype (p=0.024), extra-capsular extension (p=0.015) and the quadrant of tumor (p=0.004) were independent risk factors for N2 or N3 disease. A nomogram was developed based on these five factors. The area under the curve from the receiver operating characteristic graph was 0.830 for the training group and 0.853 for the validation group. We have developed a nomogram that uses information commonly available to accurately estimate the likelihood of N2 or N3 disease for an individual patient, which might be helpful for radiation oncologists to make a decision on regional nodal irradiation for breast cancer patients with 1-3 positive nodes but without axillary dissection.