A Dosimetric Comparison of Intensity Modulated Radiotherapy versus Three-dimensional Conformal Radiotherapy for Esophageal Carcinoma

Abstract

Purpose/Objective(s)To demonstrate the use of IMRT of esophageal cancer patients and to evaluate its dosimetric results by comparing them with 3D-CRT.Materials/MethodsNine patient cases with primary esophageal carcinoma were selected for this study, which were divided into cervical/upper thoracic esophageal cancer group, mid-thoracic group, and lower thoracic group. Each group consisted of one case with small lesion (GTV <30 cm3), one with wide lesion (width of GTV >4 cm) and one with long lesion (length of GTV >7 cm).The 3D-CRT plans using 3, 4, 5, and 6 beams (CRT3, CRT4, CRT5, and CRT6) and IMRT plans using 4, 5, 7, 9, and 11 beams (IMRT4, IMRT5, IMRT7, IMRT9, and IMRT11) were developed for each patient. The goals for IMRT plans were to ensure 95% coverage of the PTV to the prescribed dose (66 Gy at 2 Gy per fraction), minimum dose of 62.7 Gy to 99% volume of PTV, while keeping the dose delivered to lung, spinal cord, heart within normally accepted tolerances. The 3D-CRT plans were developed to have the same PTV prescription and reach similar normal tissue constraints as those of the IMRT plans. The IMRT and 3D-CRT plans were evaluated with respect to PTV coverage and dose-volumes to irradiated normal structures.ResultsNine male esophageal cancer patients with Stage IIA∼IVA disease entered this study and 81 plans were made totally. All the 3D-CRT plans were inferior to that of the IMRT plans in terms of target dose conformity in the cervical/upper thoracic group (p < 0.001), mid-thoracic group (p < 0.001) and lower thoracic group (p = 0.006). No clinically meaningful differences were observed with respect to the percentage lung volume receiving a dose below 5 Gy,10 Gy, and MLD among all the groups. In the cervical/upper thoracic group all the maximum dose (Dmax) of the spinal cord was above 45 Gy in 3D-CRT plans although no significant differences were found. In the mid-thoracic group the 3D-CRT plans were less effective in reducing the lung V20 (p = 0.002) and V25 (p = 0.024) when compared with the IMRT plans. The Dmax to the spinal cord were significantly reduced in the IMRT plans (p < 0.001) and that in 3D-CRT plans were all above 45 Gy except in CRT5. In the lower thoracic group the 3D-CRT plans were also inferior to that of the IMRT plans in terms of reducing the lung V25 (p = 0.034) and V30 (p = 0.015). Furthermore, the mean dose of heart was above 30 Gy in all 3D-CRT plans although no significant differences were observed.ConclusionsThe IMRT plans provided improvement over 3D-CRT in the treatment planning for cervical/upper, mid, and lower thoracic esophageal cancer patients in terms of PTV coverage, target dose conformity and normal tissues sparing. The IMRT plans with 5 or 7 beams could be recommended for the treatment of esophageal carcinoma considering dosimetric results and clinical practices. Purpose/Objective(s)To demonstrate the use of IMRT of esophageal cancer patients and to evaluate its dosimetric results by comparing them with 3D-CRT. To demonstrate the use of IMRT of esophageal cancer patients and to evaluate its dosimetric results by comparing them with 3D-CRT. Materials/MethodsNine patient cases with primary esophageal carcinoma were selected for this study, which were divided into cervical/upper thoracic esophageal cancer group, mid-thoracic group, and lower thoracic group. Each group consisted of one case with small lesion (GTV <30 cm3), one with wide lesion (width of GTV >4 cm) and one with long lesion (length of GTV >7 cm).The 3D-CRT plans using 3, 4, 5, and 6 beams (CRT3, CRT4, CRT5, and CRT6) and IMRT plans using 4, 5, 7, 9, and 11 beams (IMRT4, IMRT5, IMRT7, IMRT9, and IMRT11) were developed for each patient. The goals for IMRT plans were to ensure 95% coverage of the PTV to the prescribed dose (66 Gy at 2 Gy per fraction), minimum dose of 62.7 Gy to 99% volume of PTV, while keeping the dose delivered to lung, spinal cord, heart within normally accepted tolerances. The 3D-CRT plans were developed to have the same PTV prescription and reach similar normal tissue constraints as those of the IMRT plans. The IMRT and 3D-CRT plans were evaluated with respect to PTV coverage and dose-volumes to irradiated normal structures. Nine patient cases with primary esophageal carcinoma were selected for this study, which were divided into cervical/upper thoracic esophageal cancer group, mid-thoracic group, and lower thoracic group. Each group consisted of one case with small lesion (GTV <30 cm3), one with wide lesion (width of GTV >4 cm) and one with long lesion (length of GTV >7 cm).The 3D-CRT plans using 3, 4, 5, and 6 beams (CRT3, CRT4, CRT5, and CRT6) and IMRT plans using 4, 5, 7, 9, and 11 beams (IMRT4, IMRT5, IMRT7, IMRT9, and IMRT11) were developed for each patient. The goals for IMRT plans were to ensure 95% coverage of the PTV to the prescribed dose (66 Gy at 2 Gy per fraction), minimum dose of 62.7 Gy to 99% volume of PTV, while keeping the dose delivered to lung, spinal cord, heart within normally accepted tolerances. The 3D-CRT plans were developed to have the same PTV prescription and reach similar normal tissue constraints as those of the IMRT plans. The IMRT and 3D-CRT plans were evaluated with respect to PTV coverage and dose-volumes to irradiated normal structures. ResultsNine male esophageal cancer patients with Stage IIA∼IVA disease entered this study and 81 plans were made totally. All the 3D-CRT plans were inferior to that of the IMRT plans in terms of target dose conformity in the cervical/upper thoracic group (p < 0.001), mid-thoracic group (p < 0.001) and lower thoracic group (p = 0.006). No clinically meaningful differences were observed with respect to the percentage lung volume receiving a dose below 5 Gy,10 Gy, and MLD among all the groups. In the cervical/upper thoracic group all the maximum dose (Dmax) of the spinal cord was above 45 Gy in 3D-CRT plans although no significant differences were found. In the mid-thoracic group the 3D-CRT plans were less effective in reducing the lung V20 (p = 0.002) and V25 (p = 0.024) when compared with the IMRT plans. The Dmax to the spinal cord were significantly reduced in the IMRT plans (p < 0.001) and that in 3D-CRT plans were all above 45 Gy except in CRT5. In the lower thoracic group the 3D-CRT plans were also inferior to that of the IMRT plans in terms of reducing the lung V25 (p = 0.034) and V30 (p = 0.015). Furthermore, the mean dose of heart was above 30 Gy in all 3D-CRT plans although no significant differences were observed. Nine male esophageal cancer patients with Stage IIA∼IVA disease entered this study and 81 plans were made totally. All the 3D-CRT plans were inferior to that of the IMRT plans in terms of target dose conformity in the cervical/upper thoracic group (p < 0.001), mid-thoracic group (p < 0.001) and lower thoracic group (p = 0.006). No clinically meaningful differences were observed with respect to the percentage lung volume receiving a dose below 5 Gy,10 Gy, and MLD among all the groups. In the cervical/upper thoracic group all the maximum dose (Dmax) of the spinal cord was above 45 Gy in 3D-CRT plans although no significant differences were found. In the mid-thoracic group the 3D-CRT plans were less effective in reducing the lung V20 (p = 0.002) and V25 (p = 0.024) when compared with the IMRT plans. The Dmax to the spinal cord were significantly reduced in the IMRT plans (p < 0.001) and that in 3D-CRT plans were all above 45 Gy except in CRT5. In the lower thoracic group the 3D-CRT plans were also inferior to that of the IMRT plans in terms of reducing the lung V25 (p = 0.034) and V30 (p = 0.015). Furthermore, the mean dose of heart was above 30 Gy in all 3D-CRT plans although no significant differences were observed. ConclusionsThe IMRT plans provided improvement over 3D-CRT in the treatment planning for cervical/upper, mid, and lower thoracic esophageal cancer patients in terms of PTV coverage, target dose conformity and normal tissues sparing. The IMRT plans with 5 or 7 beams could be recommended for the treatment of esophageal carcinoma considering dosimetric results and clinical practices. The IMRT plans provided improvement over 3D-CRT in the treatment planning for cervical/upper, mid, and lower thoracic esophageal cancer patients in terms of PTV coverage, target dose conformity and normal tissues sparing. The IMRT plans with 5 or 7 beams could be recommended for the treatment of esophageal carcinoma considering dosimetric results and clinical practices.