To clarify the radiotherapy clinical target volume (CTV) margin needed for esophageal squamous-cell carcinoma (SCC) and gastroesophageal junction (GEJ) adenocarcinoma.

Surgical specimens of esophageal SCC (n = 34) and GEJ adenocarcinoma (n = 32) were prospectively collected and analyzed for microscopic spread along the esophagus and GEJ both proximally and distally from gross tumor and for lymph node (LN) metastasis.

For SCC, the mean microscopic spread beyond the gross tumor was 10.5 +/- 13.5 mm proximally (<30 mm in 32 of 34 cases) and 10.6 +/- 8.1 mm distally (<30 mm in 33 of 34 cases). For GEJ adenocarcinoma, the spread was 10.3 +/- 7.2 mm proximally (<30 mm in 29 of 29 cases) and 18.3 +/- 16.3 mm distally (<30 mm in 27 of 32 cases). The extent of microscopic spread of cancer was significantly associated with pathologic T stage (p = 0.012). LN metastases were observed in 12 (35%) of 34 patients with middle and lower esophageal SCC and 15 (47%) of 32 patients with GEJ adenocarcinoma.

The extent of microscopic spread within esophagus (recommended CTV margin) was <30 mm in about 94% of cases of esophageal cancer, except for distal microscopic spread in GEJ adenocarcinoma, in which 50 mm was needed to cover about 94% of cases.