Dosimetric Comparison of Treatment of Left Breast Cancer Using3-Dimention Conformal Radiotherapy Technique (3D-CRT) andIntensity-Modulated Radiotherapy Technique (IMRT)

Breast cancer is the most common malignant cancer in women, and is the second leading cause of
death from cancer in women, after lung cancer. This study compared the dose distribution of left breast as
planning target volume (PTV), ipsilateral lung, contralateral lung, heart, and contralateral breast in whole left
breast radiotherapy with two general methods, 3-dimention conformal radiotherapy technique (3D-CRT) and
intensity-modulated Radiotherapy technique (IMRT) using treatment planning system.
Computed tomography (CT) scan data of 30 patients with left breast cancer with average age of
46 years, candidates for radiotherapy of whole breast, were selected randomly. The left breast contoured as the
target and ipsilateral lung, contralateral lung, heart, and contralateral breast contoured as organs at risks
according to Radiation Therapy Oncology Group (RTOG) protocol. The 3D-CRT planned with using two
tangential opposite beams, depended to patient's anatomy with or without a wedge and using energy of 6 MV.
The IMRT treatment plan was optimized by three methods, IMRT-6Field, IMRT-7Field, and IMRT-9Field with
energy of 6 MV. Finally, the dosimetric factors of target organ and organs at risk were derived from the dosevolume
histogram (DVH) plot, and compared with each other.
Findings: The IMRT techniques increased the mean dose of all organs compared to the 3D-CRT technique.
From the dosimetric point of view, this was a good indication for target tissue. In the IMRT technique, the
volume of the ipsilateral lung that coverage the high doses decreased, and the volume that coverage the lower
doses increased compared to 3D-CRT technique. Homogeneity and conformance indexes in IMRT-9Field
method were the best, and in 3D-CRT method were the worst among all methods.
In general, the IMRT techniques are better than the 3D-CRT technique due to better coverage of
the target volume, and volume reduction of the dose-receiving organ; there are no significant differences
between the three IMRT techniques.