Determining the lymph node clinical target volume of upper esophageal carcinoma with computed tomography

Abstract

Radiation is an important modality for cervical and upper-thoracic esophageal squamous cell carcinoma (ESCC). Delineating the lymph node clinical target volume (CTVn) for EC remains a challenging task. The present paper retrospectively analyzes the distribution of affected lymph nodes of cervical and upper thoracic ESCC on CT images to provide a reference for determination of CTVn. The cases of untreated cervical or upper-thoracic ESCC patients with regional lymph node metastases at diagnosis were retrospectively analyzed. CT scans were done to assess the extent of circumferential involvement and the local-regional lymph node status. Based on the CT criteria (cervical, mediastinal and upper abdominal lymph nodes were considered to be positive for malignancy when they were larger than 8-12 mm in short-axis diameter according to different station respectively). Detailed lymph node stations were recorded for every case and the distribution information of loco-regional node metastasis for these patients was analyzed. A total of 256 patients were diagnosed with node metastasis and qualified for the study, including 206 men and 50 women (age range 37-85 years, median 60). This included 205 upper thoracic cases and 51 of cervical lesion. The length of the primary tumors ranged from 1.0 cm to 9.0 cm, median 4.5 cm. The size of the enlarged lymph nodes ranged from 0.8 to 5.0 cm median 1.4 cm, mean 1.61 cm. The number of involved stations ranged from 1 to 7 median 2. The lymph node stations, with an involved probability of 10% or more, included the upper and middle neck, supraclavicular and lower neck, upper paraesophageal and upper paratracheal area for cervical lesions, and the supraclavicular and lower neck, upper paraesophageal, upper paratracheal, lower paratracheal, aortopulmonary and subcarinal areas for upper thoracic EC, respectively. The mid-upper neck nodes were more likely to be involved in cervical EC than thoracic EC (X 2 test, p=0.000). Fewer cervical EC involved the station 7 nodes than upper thoracic EC(X 2 test, p=0.006), and the supraclavicular nodes were more often involved in cervical lesions than upper thoracic lesions (X 2 test, p=0.029). However, the abdominal nodes showed a similar possibility of involvement (X 2 test, p=0.546). Our data suggest that the periesophageal and supraclavicular stations are the predominant involved areas for cervical and upper EC cases. The neck and upper mediastinal nodal station (above the arcus aortae level) should be electively irradiated for cervical EC and the supraclavicular, upper mediastinal and subcarinal area (station 7) should be included for upper thoracic EC. This study provides complementary data for the CTVn delineation, especially for advanced stage ESCC.