Dosimetric comparison of IMRT versus 3DCRT for post-mastectomy chest wall irradiation

Purpose: To compare the dose distribution of three-dimensional conform a I radiation therapy (3DCRT) with intensity-modulated radiation therapy (IMRT) for post-mastectomy radiotherapy (PMRT) to left chest wall Materials and Methods: One hundred and seven patients were randomised for PMRT in 3DCRT group (n=64] and IMRT group (n = 43). All patients received 50 Gy in 25 fractions. Planning target volume (PTV) parameters-Dnear-max (D-2), Dnear-min (D-98), D-mean V-95 and V-107,(p-homogeneity index (HI), and conformity index (CI) were compared. The mean doses of lung and heart, percentage volume of ipsilateral lung receiving 5 Gy (V-5), 20 Gy (V-20), and 55 Gy (V-55) and that of heart receiving 5 Gy (V-5), 25 Gy (V-25), and 45 Gy (V-45) were extracted from dose-volume histograms and compared. Results: PTV parameters were comparable between the two groups CI was significantly improved with IMRT (1.127 vs 1.254, p < 0,001) but HI was similar (0.094 vs, 0,096, p = 0.83) compared to 3D CRT, IMRT in comparison to 3DCRT significantly reduced the high-dose volumes of lung (V-20, 22.09% vs. 30.18%; V-55, 5.16% vs 10.27%; p < 0 001) and heart (V-25, 4.59% vs. 9.19%, V-45, 1.85% vs. 709%; p < 0.001); mean dose of lung and heart (11.39 vs 14.22 Gy and 4.57 vs 8.96 Gy, respectively, p < 0.001) but not the low-dose volume (V-5 lung, 61 48% vs 51.05%, V, heart, 31.02% vs 23.27%, p < 0001). Conclusions: For left sided breast cancer, IMRT significantly improves the conformity of plan and reduce the mean dose and high-dose volumes of ipsilateral lung and heart compared to 3DCRT, but 3DCRT is superior in terms of low-dose volume.