Evaluation of FDG PET in early axillary lymph node response to neoadjuvant chemotherapy in locally advanced breast cancer patients

Abstract

10500 Background: Regional axillary lymph node status has remained the single most independent variable to predict prognosis both in terms of disease recurrence and survival. This study aimed to prospectively assess sequential FDG PET findings as early predictors of axillary lymph node response to neoadjuvant chemotherapy in locally advanced breast cancer patients. Methods: A total of 255 attenuation-corrected scans were obtained from 51 patients. Images were acquired with a PET/CT scanner (GE Discovery LS) following administration of FDG (5 MBq/kg) at baseline, and after the first, second, third, and sixth course of chemotherapy. Clinical examination and US were used to assess the size of axillary lymph nodes. PET data were interpreted using standardized uptake values (SUV) corrected or not for partial volume effects. Changes in the SUV were considered as surgical/histopathological responses. Results: This study focused on axillary lymph node staging, therefore, primary breast tumor data were not considered in the analysis. The sensitivity, specificity, and accuracy of axillary node staging was higher with PET (75%, 87%, 80%) than with clinical examination and US (50%, 78%, 63%, and 50%, 83%, and 65%, respectively), and even the more so when PET images were corrected for partial volume effects (86%, 83%, 84%). Significant differences between absolute FDG uptake values in responders and non-responders were observed at baseline (p < 0.05). While FDG uptake did not vary much in non-reponders, as confirmed by histopathology, it markedly decreased to baseline levels in responders (p < 10−5). Fifty percent of baseline SUV was considered the best cut-off value to distinguish responders from non-responders. The sensitivity, specificity, negative predictive value, and accuracy of FDG PET after one course of chemotherapy were respectively, 96%, 75%, 95%, and 84%. Tumor response assessment by clinical examination or US was never statistically significant whatever the cut-off. Conclusions: The pathological status of regional axillary lymph nodes in locally advanced breast cancer patients can be accurately predicted after one course of neoadjuvant chemotherapy based on FDG PET images. No significant financial relationships to disclose.