Patterns of failure after involved field radiotherapy for locally advanced esophageal squamous cell carcinoma.

Purpose: To retrospectively analyze the patterns of failure and the treatment effects of involved-field irradiation (IFI) on patients treated with locally advanced esophageal squamous cell carcinoma (ESCC) and to determine whether IFI is practicable in these patients. Methods: A total of 79 patients with locally advanced ESCC underwent three dimensional conformal (3D-CRT) or intensity modulated radiotherapy (IMRT) using IFI or elective nodal irradiation (ENI) according to the target volume. The patterns of failure were defined as local/regional, in-field, out-of-field regional lymph node (LN) and distant failure. With a median follow-up of 32.0 months, failures were observed in 66 (83.6%) patients. Results: The cumulative incidence of local/regional failure (55.8 vs 52.8%) and in-field regional lymph node failure (25.6 vs 19.4%) showed no statistically significant difference between the IFI and the ENI group (p=0.526 and 0.215, respectively). Out-of-field nodal relapse rate of only 7.0% was seen in the IFI group. Three-year survival rates for the ENI and IFI group were 22.2 and 18.6%, respectively (p=0.240), and 3-year distant metastasis rates were 27.8 and 32.6%, respectively (p=0.180). The lung V-10, V-20, V-30 and mean lung dose of the ENI group were greater than those of the IFI group, while the mean lung dose and V10 had statistically significant difference. Conclusions: The patterns of failure and survival rates in the IFI group were similar as in the ENI group; the regional recurrence and distant metastasis are the main cause of treatment failure. IFI is feasible for locally advanced ESCC. Further investigation is needed to increase local control and decrease distant metastasis in these patients.