FDG PET is used in staging, early prediction of treatment response, monitoring metastatic tumours and in disease status assessment post completion of treatment. In patients undergoing upfront surgery, a significant standardized uptake value (SUV) is associated with pathological node positivity. In patients receiving anterior chemotherapy, studies have shown that a reduction in size and SUV of primary tumour or involved node predicts response to therapy. However based on our observation, the predictive value of PETCT appeared to differ between the upfront setting and post-neoadjuvant chemotherapy (NACT) setting. Our study compares the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of FDG-PET in predicting pathological axillary nodal involvement in 50 upfront surgery and 50 post-NACT patients.
This study was conducted between the years 2015 to 2016. Clinical, histopathological and radiological details were obtained from patient records. 50 upfront surgery and 50 post-NACT patient details were reviewed for PETCT nodal status and histopathological nodal status and the following parameters analysed. 1)Sensitivity; 2)Specificity; 3)Positive Predictive Value; 4)Negative Predictive Value
In upfront surgery cases the total number of TP was 21, FP was 2, FN was 12 and TN was 15. In post NACT setting, it was 5, 1, 10 & 34 respectively.
Upfront PETCT Post NACT PETCT Sensitivity 63.6% 33.3% Specificity 88.2% 97.1% Positive Predictive Value 91.3% 88.3% Negative Predictive Value 55.3% 77.2%
Although metabolic response monitoring post chemotherapy is a useful tool,the sensitivity appears to be lower in predicting pathological node positivity. That is, the proportion of patients with positive pathological node having PET positivity appears to be lower. A practical application of the same would be, to complete all cycles of chemotherapy prior to surgery, irrespective of an interim PETCT complete nodal response, to attain maximal Pathological Complete Response rates.To conclude, the rate of PETCT predictivity of pathological axillary nodal positivity appears to differ between upfront surgery and post-NACT setting.
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All authors have declared no conflicts of interest.