The axillary lymph node to primary breast tumor SUV ratio on FDG-PET/CT in FDG avid primary breast cancers: Could predict the necessity for axillary lymph node dissection

Abstract

Background: Emerging evidence has indicated that breast cancer patients with a low axillary burden do not benefit from sentinel lymph node biopsy. Thus, to specifically identify more than 3 nodes-positive patients who can proceed directly to axillary lymph node(ALN) dissection, and avoid unnecessary surgical procedures, accurate preoperative detection by radiologic assessment would be anticipated. In this study, we evaluated the usefulness of ALN to primary breast tumor SUV ratio (determined by 18F-FDG PET/CT) and MRI for predicting the need for ALN dissection in breast cancer surgery. Method: Three hundred sixteen consecutive female patients with primary breast cancer were enrolled in this retrospective study between January 2012 and December 2016. All patients underwent preoperative 18F-FDG PET/CT, MRI, and surgical resection without neoadjuvant chemotherapy.The ALN to primary breast tumor SUV ratios(LN/T ratios) were calculated, and optimal cutoff values were determined by receiver operating characteristic curve analysis for predicting the presence of ≥3 ALN metastasis. The diagnostic performances of 18F-FDG PET/CTLN/T ratio and MRI for the prediction of ≥3 ALN metastasis were determined by sensitivity, specificity, and diagnostic odds ratio(DOR). Subgroup analysis of those for FDG avid cancers were performed. Result: Of the 316 patients, 36(11.4%) showed involvement of ≥3 ALNs, and 101(32%) had one or more metastatic lymph nodes. The mean SUV of the primary tumor in the 316 patients was 3.9, ranging from 0 to 26.6, while the mean SUV of the ALN was 0.81, ranging from 0 to 21.9. Axillary 18F-FDG uptake was positive in 75(23.7%) patients and optimal criteria of LN/T ratio for detecting the needs for ALN dissection was 0.3 determined by ROC analysis.MRI showed findings of suspicious ALN involvement in 147(46.6%) patients. The sensitivity and specificity of MRI were 0.89 and 0.56, while those of PET/CTLN/T ratio were 0.69 and 0.87. In the receiver operating characteristic(ROC) analysis, the area under the curve(AUC) for MRI and PET/CTLN/T ratio was 0.756 (0.682-0.829, 95% confidence interval), and 0.817(0.733-0.900, 95% confidence interval). Further analysis of the DOR for MRI showed a value of 10.37 and for PET/CTLN/T ratio the DOR was 9.7. But, in a subgroup of patients with FDG-avid primary tumor(FDG above 3.9, n=108), the area under the curve was improved to 0.896 (0.817-0.975, 95% confidence interval) for PET/CTLN/T ratio, while those of MRI was worsened. (0.681, 0.569- 0.793., 95% CI) DOR value of PET/CTLN/T ratio for FDG avid cancers was 25.68 and their sensitivity and specificity were 0.83 and 0.84 each. Conclusion: In FDG avid primary breast cancer, PET/CTLN/T ratio could predict need for ALN dissection with higher accuracy than MRI. PET/CT has high potential for being used as a non-invasive imaging diagnostic technique identifying ≥3 ALNs metastases.