Dosimetric Comparison of Conventional Radiation Therapy, 3-dimensional Conformal Radiation Therapy and Intensity Modulated Radiation Therapy for Non-Hodgkin Lymphoma in Pelvis

Abstract

To investigate the potential advantage and dose distribution for intensity-modulated radiation therapy in the treatment of non-Hodgkin lymphoma involving the pelvic with regards to organ-at-risk (OAR) avoidance. Eight patients with large B-cell lymphoma were evaluated. For each patient, intensity-modulated radiation therapy, conventional parallel-opposed(AP-PA), and three dimensional conformal radiation therapy(3D-CRT) plans were designed using 6-MV X-rays to deliver doses of 45Gy. The planning target volume and organ-at-risk (small bowel, rectum, bladder and femoral head) dose-volume histograms (DVHs) were analyzed. The inhomogeneity coefficient(IC) of different plans, the PTV receiving 95% the prescription dose(D95), the normal tissue complication probability(NTCP) and the dose volume parameters for the OARs were calculated. The planning target volume coverage was improved by using IMRT compared with AP-PA, but was not different from that obtained by 3D-CRT (ICAP-PA = 0.16 vs. IC3D-CRT=0.11 vs. ICIMRT=0.10, P<0.05). The average volumes of small bowel irradiated to 45Gy were 68±21cc, 98±29cc and 261±17cc in IMRT, 3D-CRT and AP-PA, respectively. The V40 and V45 of bladder, rectum and femoral head were significantly reduced by IMRT compared with 3D-CRT and AP-PA. There were no statistical differences between the three techniques with respect to OARs receiving low radiation doses. Compared with AP-PA, 3D-CRT and IMRT are superior in sparing OARs, with adequate coverage of planning target volume.