Involved Field Radiation Therapy (IFRT) with Omission of Prophylactic Nodal Irradiation in Locally Advanced Squamous Carcinoma of the Thoracic Esophagus: A Retrospectively Comparative Analysis of Clinical Outcomes

Abstract

Involved field radiotherapy (IFRT) omitting prophylactic radiation to clinically uninvolved lymph nodes has raised concerns for increased nodal failures. This retrospective cohort analysis evaluated the failure patterns and survival of locally advanced squamous carcinoma of the thoracic esophagus patients treated with elective nodal irradiation (ENI) or IFRT at a single institution. We assessed all locally advanced esophageal squamous carcinoma (LA-ESCC) patients treated with definitive concurrent chemoradiotherapy from January 2003 to January 2013. Thoracic LA-ESCC patients with well-documented clinical reports available were included whether they underwent ENI or IFRT. Survival time was calculated using Kaplan-Meier methodology. The cumulative incidence of failure patterns was determined according to the first sites of failure including local, regional, distant failure patterns. Regional recurrences were classified as “PTVifi,” “Out-PTVifi in-PTVeni failure,” “Out-PTVeni failure” through comparing the three-dimensional localization images with tumor recurrence images. A total of 313 thoracic LA-ESCC patients met the inclusion criteria. Similar response rates were observed in two groups (P = 0.204). No significant difference existed in 1-, 2-, and 3-year survival rates (P = 0.101) while patients of IFRT group exhibited better 5-year survival rate (P= 0.042). Local failure rate ranked the first in both groups. Either isolated out-PTVifi in-PTVeni failure rates (7% IFRT vs. 5% ENI) or Out-PTVifi in-PTVeni failure simultaneously with other failures rates (11% IFRT vs. 14% ENI) showed no significant difference in two groups. IFRT patients demonstrated a significantly lower risk of high-grade (Grade ≥3) esophagitis (P = 0.03), lung injury (P = 0.011), and bone marrow suppression (P = 0.041). Omission of prophylactic nodal irradiation could significantly alleviate acute toxicities without impairing the eventual treatment outcome, suggesting that IFRT may allow for integration of concurrent systemic chemotherapy in a greater proportion of patients especially in thoracic LA-ESCC cases.