Target delineation for esophageal cancer

Although esophagectomy remains the treatment of choice for resectable tumors, the combination of chemoradiotherapy and surgery has become a common treatment of esophageal carcinoma. The most common combination is preoperative concurrent chemoradiation therapy followed by esophagectomy. For patients with unresectable tumors, chemoradiation without surgery is the standard of care. Therefore, radiation therapy is an important component of curative treatment for patients with esophageal carcinoma. The success of radiation depends on accurate delineation of gross tumor volume and adequate coverage of clinical target volume to ensure accurate delivery of radiation. Accurate delineation of gross tumor volume of esophageal cancer depends on positive findings obtained from all diagnostic modalities used in pretreatment evaluation, including barium esophagogram, endoscopic examination and biopsy, endoscopic ultrasonography, computed tomography, and positron emission tomography, whichever is positive. A wall thickness of more than 0.5 cm measured on computed tomography should be considered abnormal and included in the gross target volume. The clinical target volume is an area of debate and meticulous documentation of subclinical extension of the disease on pathologic examination will help to clarify this issue. The planning target volume should include 5-cm proximal and distal margins and 2-cm radial margins from the gross tumor. Regional lymph nodes should be included in the clinical target volume. Active investigation of respiratory and peristalsis tumor motion is warranted in esophageal cancer. Molecular imaging is a new diagnostic and therapeutic modality that offers great potential, and clinical trials testing these new imaging modalities have been initiated.