[Qualitative and quantitative PET/MRI in the evaluation of axillary lymph node metastasis in patients with breast cancer].

Objective: To investigate the value of qualitative and quantitative PET/MRI in the evaluation of axillary lymph node metastasis in patients with breast cancer. Methods: A total of 33 patients with breast cancer underwent preoperative PET/MRI examinations in Jingling Hospital from February to August in 2022 were retrospectively collected. All these patients were female, aged from 34 to 73 (51.4±11.3) years. Histopathological results and follow-up data were deemed as the referent standard, and the images were independently evaluated by two experienced breast imaging radiologists. The qualitative PET/MRI evaluation procedures were designed to evaluated the MRI alone to classify the axillary lymph nodes firstly, and then, the axillary lymph nodes status was reclassified by combining MRI and PET images. The net reclassification improvement index (NRI) was calculated using the R Programming Language (RStudio). The quantitative PET/MRI evaluation of the maximum standard uptake value (SUVmax) of axillary lymph nodes were measured by two radiologists, respectively, and the average value was compared with the referent standard to conduct a receiver operating characteristic (ROC) curve to select the optimal cutoff value of SUVmax. Based on the cutoff value and MRI classification results, axillary lymph nodes status was divided into quantitative PET/MRI positive or negative. The sensitivity, specificity and accuracy of MRI and quantitative PET/MRI in evaluating axillary lymph node metastasis were compared, and the area under the ROC curve (AUC) was compared. Results: There was no significant difference in sensitivity, specificity and accuracy between MRI and quantitative PET/MRI in evaluating lymph node metastasis of breast cancer (81.82% vs 95.46%; 81.82% vs 100%; 81.82% vs 96.97%) (all P>0.05). The AUC had a statistically significant difference [0.82 (0.65 to 0.93) vs 0.98 (0.85 to 1.00), P=0.026)]. According to the referent standard, in the 11 cases without ipsilateral axillary lymph node metastasis, the SUVmax was 0.83±0.18, while in the 22 cases with ipsilateral axillary lymph node metastasis, the SUVmax was [4.36 (1.77, 5.85)]. Compared with MRI alone, the NRI of qualitative PET/MRI in evaluating lymph node metastasis was 36.36% (P=0.021). Conclusion: Compared with MRI alone, quantitative PET/MRI has a higher AUC for evaluating axillary lymph node metastasis in patients with breast cancer, and qualitative PET/MRI had a better reclassification power in the evaluation of axillary lymph node metastasis.