Variations in positron emission tomography-computed tomography findings for patients receiving neoadjuvant and non-neoadjuvant therapy for non-small cell lung cancer.

BACKGROUND: The aims of this study were to predict locoregional lymph node (LN) metastases using positron emission tomography-computed tomography (PET-CT) and investigate variations in PET-CT findings for patients receiving neoadjuvant (NT) and non-neoadjuvant (non-NT) for non-small cell lung cancer (NSCLC).

METHODS: Data from 578 consecutive patients from January 2010 to December 2015 who met this study inclusion criteria were retrospectively reviewed. All patients underwent curative and complete resections for NSCLC in a Korean hospital. We analyzed the associations between maximum standard uptake value (SUVmax) and pathological stage, compared disease-free survival (DFS) and overall survival (OS), investigated relationships among SUVmax values, evaluated LN status and compared pathologically negative and positive LNs by SUVmax, and assessed the influence of neoadjuvant therapy on SUVmax. All LNs were analyzed separately for N1 and N2.

RESULTS: (I) For non-NT, we found significantly positive associations between pathological stage and SUVmax (tumor, N1 LN, and N2 LN, all P<0.001). For NT, we found positive correlations between pathological stage and tumor and N2 LN SUVmax, except for N1 LN (tumor P=0.005, N1 LN P=0.981, N2 LN P=0.045); (II) for non-NT, the low SUVmax group had higher DFS and OS than the high SUVmax group (DFS: tumor SUVmax P<0.001, N1 LN SUVmax P=0.002, N2 LN SUVmax P=0.027; OS: tumor SUVmax P<0.001, N1 LN SUVmax P=0.006, N2 LN SUVmax P=0.006). For NT, the low SUVmax group had nonsignificantly higher DFS and OS than the high SUVmax group. When age, sex, and SUVmax were equal, pathological stages were significantly higher for NT than non-NT (P<0.001). Non-NT had significantly higher DFS (P=0.001) and OS (P=0.024) than NT; (III) for non-NT, tumor, N1 LN, and N2 SUVmax were positively associated (all P<0.001). For NT, tumor and N2 SUVmax (P<0.001), and N1 and N2 SUVmax (P=0.025) correlated positively; tumor and N1 LN SUVmax did not (P=0.911); (IV) for non-NT, there was significant cutoff values for prediction of LN metastases using both tumor and LN SUVmax (N1 LN: tumor SUVmax cutoff 5.95, sensitivity 66.3%, specificity 66.0%, area =0.748, P<0.001; N1 LN SUVmax cutoff 2.05, sensitivity 57.83%, specificity 66.43%, area =0.676, P<0.001) (N2 LN: tumor SUVmax cutoff 5.95, sensitivity 63.04%, specificity 63.95%, area =0.726, P<0.001; N2 LN SUVmax cutoff 2.05, sensitivity 65.22%, specificity 69.96%, area =0.678, P<0.001). For NT, no SUVmax values significantly predicted LN metastases; () Pathologically malignant and benign LN SUVmax after neoadjuvant therapy were not different (N1 LN P=0.570, N2 LN P=0.105). For non-NT, pathologically malignant LN SUVmax was significantly higher than pathologically benign LN SUVmax (N1 LN P<0.001, N2 LN P=0.001).

CONCLUSIONS: This study showed variations in PET-CT findings for NT and non-NT, which should be verified for evaluation and management, especially for surgery planning. SUV max is not a reliable predictor of lymphatic involvement after neoadjuvant therapy in patients with NSCLC. Surgery should not be withheld or delayed based on lack of knowledge about variations in PET-CT findings, which must be interpreted in conjunction with other conditions. Further studies on interpretation of PET-CT findings, especially for NT, are needed for better management and prognosis.