Dosimetric Evaluation of Intensity Modulated Radiotherapy and Three-Dimensional Conformal Radiotherapy Treatment Plans for Prostate Cancer

OBJECTIVE We evaluated the homogeneity index and conformity index using intensity modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT) treatment plans in prostate cancer. METHODS Twenty treatment plans for ten patients were created using 3D-CRT of four-fields with gantry angles of 0 degrees, 90 degrees, 180 degrees, and 270 degrees; and IMRT of five-fields with gantry angles of 0 degrees, 72 degrees, 144 degrees, 216 degrees, and 288 degrees on an Eclipse Treatment Planning System (version 15.6). The volume of reference isodose, target volume, maximum isodose in the target, reference isodose, dose at 95% of planning target volume (PTV), dose at 2%, 5%, and 98% of PTV, and prescribed dose were collected from the dose volume histogram of each plan. The conformity index and homogeneity index (HI) were then calculated. The doses of the organs at risk were also collected and evaluated. RESULTS The HI of the twenty patients who underwent the treatment plan with 3D-CRT was 1.088 +/- 0.03, which shows good homogeneity, but less homogeneity when compared with plans done with IMRT (1.072 +/- 0.02). CONCLUSION The use of IMRT treatment plan for prostate cancer proved to be superior over 3D-CRT in terms of conformity and homogeneity, as well as sparring dose to organ at risk.