Radiation dose to the lymph drainage area in esophageal cancer with involved-field irradiation

Abstract

Abstract. The aim of this study was to quantify the radiation dose to the corresponding lymph drainage area in esophageal cancer using three-dimensional conformal radiation therapy (3D-CRT) with involved-field irradiation (IFI) and to analyze associated factors. A retrospective analysis of 81 patients with esophageal cancer was conducted. According to the location of the lesions, the lymph drainage area was delineated and the dosimetric parameters were calculated. The 1-, 3-, 5-and 8-year survival rates of the patients were 67.90, 33.33, 20.99 and 11.11%, respectively. Based on the dose-volume histogram in the treatment plan, we calculated the volume percentage of the planning target volume including clinically positive lymph nodes (PTV-N) receiving radiation doses of 30, 35, 40, ). The median values of V PTV-N30-50 were 73, 70, 67, 64 and 58%, respectively. The prescribed dose size exhibited no correlation with V PTV-N30-35 , but did exhibit a significant correlation with V PTV-N40-50 ; the radiation field was not correlated with V PTV-N30-45 , but exhibited a significant correlation with V PTV-N50 ; the length of the lesion on esophageal barium meal X-ray and the PTV were significantly correlated with V PTV-N30-50 . The analysis of variance revealed that the V PTV-NX value in the upper thoracic segment was higher compared with that in the middle and lower thoracic segments; V PTV-N30-35 values differed significantly according to the different locations of the lesions, whereas V PTV-N40-50 values exhibited no significant differences. The value of V PTV-NX exerted no significant effect on long-term patient survival. Therefore, the corresponding lymph drainage area of esophageal cancer is subjected to a certain radiation dose when patients undergo 3D-CRT with IFI, which may play a role in the prevention of regional nodal metastasis. However, this hypothesis requires confirmation by further clinical studies. IntroductionThere is significant controversy regarding target region delineation by esophageal cancer radiotherapy in different regions. In the RTOG85-01 randomized trial (1), irradiation of the entire esophagus for esophageal cancer was recommended. In the RTOG94-05 trial (2), an area with a margin of 2-5 cm surrounding the gross tumor volume (GTV) was defined as the clinical target volume (CTV). The supraclavicular nodes were included only when the tumor was located in the cervical esophageal area. However, the results of these two trials were not satisfactory, as the survival and local control rates did not improve significantly. In the RTOG01-33 trial (3), three-dimensional conformal radiation therapy (3D-CRT) technology was applied. The CTV included a 3-cm margin around the GTV, while the planning target volume (PTV) included a margin of ≤2 cm around the CTV. Over the last few years, an increasing number of studies have been conducted on elective nodal irradiation (ENI) for esophageal cancer; however, their conclusions have been inconsistent. It was previously reported that, compared with involved-field ...