Dosimetric comparison of intensity modulated pelvic radiotherapy with 3D conformal radiotherapy in patients with gynecologic malignancies

Abstract

Purpose: Before initiating an intensity modulated radiotherapy (IMRT) program for gynecologic malignancies we prospectively evaluated the potential benefits of IMRT by dose volume histogram comparison of IMRT and 3D conformal radiotherapy plans. Methods: Plans of ten consecutive patients with cervical and endometrial cancer were evaluated. For each patient a 4-field box technique was compared to an IMRT plan. Both plans were normalized to deliver 50.4 Gy to the PTV in six patients and 45 Gy in the remaining four. Isodose distributions and dose volume histograms were compared in seven dose levels. Results: IMRT reduced the volume of small bowel receiving more than 45 Gy in all patients. The average absolute volume of small bowel receiving 45 Gy was significantly reduced from 318 cc to 33 cc. No significant increase in the volume of small bowel receiving less than 20 Gy was observed. Rectum, bladder and bone marrow volumes receiving high doses were also significantly reduced with IMRT. Conclusions: IMRT significantly reduces the volume of normal tissues irradiated to high doses Without compromising the target coverage. This may potentially lead to a reduction in treatment related toxicities.