Dosimetric comparison between three-dimensional conformal and intensity-modulated radiotherapy for thymic tumors

Although planning studies have compared three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) for lung cancer, data for thymic tumors remain limited despite consensus guidelines favoring IMRT over 3D-CRT. This study compared 3D-CRT and IMRT regarding their ability to reduce radiation doses to normal tissues surrounding thymic tumors. We retrospectively generated 3D-CRT and IMRT treatment plans for 13 patients with thymic tumors. All plans were prescribed 60 Gy in 30 fractions. Dose–volume parameters were compared using the Wilcoxon signed-rank test; with D mean representing the mean irradiated dose to the structure and V n Gy as the percentage of volume receiving at least n Gy. IMRT significantly reduced the D mean of the heart (9.0 Gy, range 0.5–23.0 vs. 10.6 Gy, range 0.4–26.0; p = 0.003) and esophagus (13.8 Gy, range 5.5–22.8 vs. 18.3 Gy, range 9.8–26.0; p = 0.001) compared with 3D-CRT. The lung dose parameters, including D mean , V 20Gy , and V 5Gy , did not differ significantly between the two modalities. IMRT is more useful than 3D-CRT for reducing radiation doses to normal tissues surrounding thymic tumors, such as the heart and esophagus. • IMRT improves target coverage compared with 3D-CRT in thymic tumors • IMRT significantly reduces cardiac and esophageal radiation dose • Lung dose parameters are comparable between IMRT and 3D-CRT • IMRT may be appropriate for thymic tumors when feasible