Relative metabolic tumor burden is associated with residual lymph node status after neoadjuvant chemoradiotherapy in locally advanced esophageal cancer

Extended lymph node involvement could indicate limited survival benefit from neoadjuvant chemoradiotherapy with surgery in resectable locally advanced esophageal cancer. However, the threshold of node involvement is unclear.

We retrospectively measured and calculated metabolic parameters derived from ¹⁸F-FDG PET/CT of the patients with nCRT and surgery. The parameters included metabolic tumor volume of the whole body (MTVwb), of the primary tumor (MTVp), of the lymph nodes (MTVn), and relative metabolic tumor burden (R-MTB, defined as the ratio of MTVwb and MTVp).

A total of 67 patients were enrolled in the study. The MTVp with thresholds as 3.0, 3.5, 4.0, 4.5 and 5.0 were significantly correlated with clinical T categories (Spearman’s rank correlation coefficient, all P < 0.0001) and clinical tumor length categories (Spearman’s rank correlation coefficient, all P ≤ 0.005). However, the MTVn were marginally correlated with clinical lymph node categories (P = 0.023). Among the 31 (31/67, 46.3%) patients with MTVn as 0 (R-MTB as 100.00%), 5 (5/5, 100.0%) were initially restaged as cLym− (MTVn as 0, R-MTB as 100.00%), while 26 (26/62, 41.9%) were initially restaged as cLym + (MTVn > 0, R-MTB > 100.00%). After nCRT, 43 (64.2%) patients achieved ypN0. The univariate and multivariate regression revealed that R-MTB (≤ 106.00% vs. > 106.00%) was an independent factor associated with ypN + status (OR 0.093, 95%CI 0.023–0.378, P = 0.001).

The preliminary study revealed a great heterogeneity in clinical lymph node categories in esophageal cancer. It suggested that R-MTB was significantly associated with ypN status after neoadjuvant chemoradiotherapy in locally advanced esophageal cancer. The findings with the indications needed to be further studied in a prospective study with a large patient cohort.