Relative tumor volume is a better independent prognostic factor in esophageal squamous cell carcinoma: Results of a retrospective study

The present study is to evaluate the significance in prognosis of relative tumor volume (RTV) in patients with non-resectable esophageal squamous cell carcinoma (ESCC) treated by definitive radiotherapy alone or in combination with chemotherapy. Fifty-eight consecutive patients with ESCC in UICC stage I to IV were retrospectively analyzed. Relative primary gross volume (RGTVp) was defined as primary gross volume (GTVp) divided by body volume. Relative primary gross volume for lymph nodes (RGTVnd) was defined as primary gross volume for lymph nodes (GTVnd) divided by body volume. The relationships were analyzed between overall survival (OS), disease free survival (DFS), local recurrence-free survival (LRFS), distant metastasis-free survival (DMFS), and RGTVp (RGTVnd) in univariate and multivariate analyses. The cut-off values of 0.947 and 0.007 were determined for RGTVp and RGTVnd, respectively. The 3-year OS, DFS, and LRFS for patients with RGTVp ≤ 0.947 vs RGTVp > 0.947 was 65.4% vs 25.0% (P = .001), 46.2% vs 12.5% (P = .002), and 90.1% vs 42.0% (P < .001). RGTVp was an independent risk factor for OS (P = .046), DFS (P = .015) and LRFS (P = .032), but showed no association with DMFS in univariate and multivariate analyses. The 3-year DFS and DMFS for patients with RGTVnd ≤ 0.007 vs RGTVnd > 0.007 was 44.4% vs 20.0% (P = .023), and 62.9% vs 24.6% (P < .004). RGTVnd was associated with DMFS (P = .012) in multivariate, but showed no associated with DFS. The present study demonstrates that RTV was an independent factor relevant to prognosis for ESCC. It provides new clinical basis for personalized therapeutic regimens and might be included in the staging system.