Document Type : Research Articles
Division of Radiotherapy, Department of Radiology, Srinagarind Hospital, Faculty of Medicine, Khon Kaen University, Thailand.
Objectives:To compare different radiotherapy planning techniques for breast cancer after breast conserving surgery.
Materials and methods: Eighteen patients with breast cancer who underwent breast conserving surgery were selected.
For each patient four different whole breast irradiation techniques including Tan, fIMRT, iIMRT and VMAT were
compared to the conventional tangential technique (Tan). Results: Mean maximum point dose (Dmax) for Tan, fIMRT,
iIMRT and VMAT were 110.17% (±1.87), 105.89% (±1.13), 106.47% (±0.92) and 106.99% (±1.16) (p<0.001). Mean
minimum point dose (Dmin) from Tan was 84.02% (±3.68) which was significantly higher than those from fIMRT,
iIMRT and VMAT which were 76.57% (±11.4), 67.69 %( ±19.20) and 80.69% (±7.06) (p<0.001). Only the mean
V95 of fIMRT was significantly less than Tan (p=0.01). Mean percentage of volume receiving ≥ 20 Gy (V20Gy) and
mean doses of the ipsilateral lung were 17.09% and 953.05 cGy, 16.60% and 879.20 cGy, 14.79% and 772.26 cGy,
15.32% and 984.34 cGy for Tan, fIMRT, iIMRT and VMAT. Only iIMRT had a significantly lower mean V20Gy and
the mean dose to ipsilateral lung in comparison with Tan. Significantly, high mean doses to the contralateral breast
(498.07 cGy, p<0.001) were observed in VMAT. Conclusion: The conventional tangential technique provides adequate
dose coverage but resulted in high dose-volumes. The iIMRT and fIMRT had significantly smaller high dose-volumes
and better conformity. VMAT demonstrated excellent dose homogeneity and conformity but an increased low-dose
volume outside the target should be of concern.