Application of serial section method to determine the radiotherapy target volume for esophageal squamous carcinoma

The three-dimensional conformal radiotherapy (3D CRT) plays an important role in the combination treatment of esophageal carcinoma. However, an accurate estimation of the clinical target volume (CTV) of esophageal squamous carcinoma (ESCC) by 3D CRT is still problematic. This study aimed to provide reference values for CTV estimation. The serial section method was applied to observe the range of the microscopic spread proximally and distally from the tumor. Further, relationships between clinicopathological features and the microscopic spread were analyzed. The positive ratio of the proximal microscopic spread was significantly higher than in the distal spread, especially in the specimens sampled 1 and 2 cm away from the tumor (p < 0.05). Probability of infiltration and metastases was still high in the proximal "3 cm" and distal "4 cm" groups, and became much lower in more distant specimens. Further, ESCC tended to exhibit stronger ascending invasion ability. A single factor analysis showed that tumors with the length of longer than 5 cm, poorer differentiation, lymph nodes metastasis, and more aggressive phase had significantly higher microscopic spread ratio (p < 0.05). A multiple factors analysis showed that differentiation degree and tumor length were the major factors affecting the microscopic spread of ESCC. In conclusion, to cover 95 % of the microscopic spread, a proximal margin of 3.0 cm and a distal margin of 4.0 cm are needed. In order to cover 90 %, proximal and distal 3-cm margins are needed. Clinicopathological features of patients can affect the range of the microscopic spread.