Dosimetric Comparison Study Between Intensity Modulated Radiation Therapy And Three-Dimensional Conformal Proton Therapy For Treatment Of Cervical Cancer

Purpose/Objective(s)To compare intensity modulated radiation therapy (IMRT) with 3D conformal proton therapy (3D-CPT) in the treatment of cervical cancer. In particular, each technique's ability to spare pelvic bone marrow (PBM) was of primary interest in this study.Materials/MethodsA total of 6 cervical cancer patients (3 postoperative and 3 intact) were planned and analyzed. The clinical target volume consisted of the pelvic and pre-sacral lymph nodes, uterus, cervix, upper vagina, and parametrial tissue. Normal tissues included bowel, rectum, bladder, and pelvic bone marrow (including lumbosacral spine, os coxae, and proximal femora). All plans had uniform 7-mm CTV-PTV margin and were normalized to cover the 95% PTV with 99% isodose (prescription dose = 45 Gy). During both IMRT and 3D-CPT planning, a particular emphasis was placed on the optimal sparing of PBM while maintaining specified target coverage. For IMRT, non-equidistant, coplanar, eight-field sliding window technique was used. For 3D-CPT, a uniform scanning technique was utilized with three-field non-coplanar beam arrangement designed for PBM sparing and clinical practicality. Dose-volume histograms (DVH) were analyzed for comparison between the two treatment techniques.ResultsThe overall PTV and PBM volumes were 1,035.9 ± 192.2 cc and 1,151.4 ± 198.3 cc, respectively. In terms of uniformity of PTV coverage, 3D-CPT was significantly superior to IMRT (V45 Gy = 95.0 and 80.3%, respectively) and in reducing the lower dose to PBM, small bowel, and bladder (i.e., V30 Gy or less). Particularly in PBM, average V10 and V20 Gy reductions of 11.1% and 7.6%, respectively, were observed. However, in the higher dose range, IMRT provided better sparing (>V30 Gy). For example, in small bowel and bladder, average reductions in V45 Gy of 6.9% and 18.5%, respectively, were observed compared to 3D-CPT. In addition, in the case of rectum, IMRT provided better sparing in all dose ranges with 22.1% reduction in V45 Gy. This pattern was shown to be consistent across the post-op and intact-cervix cases examined.ConclusionsThe goal of this study was to explore techniques that particularly minimized low-dose in PBM, in light of the recent findings that showed association of V10 and V20 Gy with acute hematologic toxicity in patients undergoing concurrent chemotherapy. Due to its physical characteristics (i.e., low entrance dose and Bragg peak) of protons, 3D-CPT showed superior sparing in the low dose range as well as target coverage uniformity. However, IMRT showed favorable sparing of all critical structures at higher doses. Therefore, further studies are warranted to exploit the usefulness of protons for other planning/treatment objectives as well. Purpose/Objective(s)To compare intensity modulated radiation therapy (IMRT) with 3D conformal proton therapy (3D-CPT) in the treatment of cervical cancer. In particular, each technique's ability to spare pelvic bone marrow (PBM) was of primary interest in this study. To compare intensity modulated radiation therapy (IMRT) with 3D conformal proton therapy (3D-CPT) in the treatment of cervical cancer. In particular, each technique's ability to spare pelvic bone marrow (PBM) was of primary interest in this study. Materials/MethodsA total of 6 cervical cancer patients (3 postoperative and 3 intact) were planned and analyzed. The clinical target volume consisted of the pelvic and pre-sacral lymph nodes, uterus, cervix, upper vagina, and parametrial tissue. Normal tissues included bowel, rectum, bladder, and pelvic bone marrow (including lumbosacral spine, os coxae, and proximal femora). All plans had uniform 7-mm CTV-PTV margin and were normalized to cover the 95% PTV with 99% isodose (prescription dose = 45 Gy). During both IMRT and 3D-CPT planning, a particular emphasis was placed on the optimal sparing of PBM while maintaining specified target coverage. For IMRT, non-equidistant, coplanar, eight-field sliding window technique was used. For 3D-CPT, a uniform scanning technique was utilized with three-field non-coplanar beam arrangement designed for PBM sparing and clinical practicality. Dose-volume histograms (DVH) were analyzed for comparison between the two treatment techniques. A total of 6 cervical cancer patients (3 postoperative and 3 intact) were planned and analyzed. The clinical target volume consisted of the pelvic and pre-sacral lymph nodes, uterus, cervix, upper vagina, and parametrial tissue. Normal tissues included bowel, rectum, bladder, and pelvic bone marrow (including lumbosacral spine, os coxae, and proximal femora). All plans had uniform 7-mm CTV-PTV margin and were normalized to cover the 95% PTV with 99% isodose (prescription dose = 45 Gy). During both IMRT and 3D-CPT planning, a particular emphasis was placed on the optimal sparing of PBM while maintaining specified target coverage. For IMRT, non-equidistant, coplanar, eight-field sliding window technique was used. For 3D-CPT, a uniform scanning technique was utilized with three-field non-coplanar beam arrangement designed for PBM sparing and clinical practicality. Dose-volume histograms (DVH) were analyzed for comparison between the two treatment techniques. ResultsThe overall PTV and PBM volumes were 1,035.9 ± 192.2 cc and 1,151.4 ± 198.3 cc, respectively. In terms of uniformity of PTV coverage, 3D-CPT was significantly superior to IMRT (V45 Gy = 95.0 and 80.3%, respectively) and in reducing the lower dose to PBM, small bowel, and bladder (i.e., V30 Gy or less). Particularly in PBM, average V10 and V20 Gy reductions of 11.1% and 7.6%, respectively, were observed. However, in the higher dose range, IMRT provided better sparing (>V30 Gy). For example, in small bowel and bladder, average reductions in V45 Gy of 6.9% and 18.5%, respectively, were observed compared to 3D-CPT. In addition, in the case of rectum, IMRT provided better sparing in all dose ranges with 22.1% reduction in V45 Gy. This pattern was shown to be consistent across the post-op and intact-cervix cases examined. The overall PTV and PBM volumes were 1,035.9 ± 192.2 cc and 1,151.4 ± 198.3 cc, respectively. In terms of uniformity of PTV coverage, 3D-CPT was significantly superior to IMRT (V45 Gy = 95.0 and 80.3%, respectively) and in reducing the lower dose to PBM, small bowel, and bladder (i.e., V30 Gy or less). Particularly in PBM, average V10 and V20 Gy reductions of 11.1% and 7.6%, respectively, were observed. However, in the higher dose range, IMRT provided better sparing (>V30 Gy). For example, in small bowel and bladder, average reductions in V45 Gy of 6.9% and 18.5%, respectively, were observed compared to 3D-CPT. In addition, in the case of rectum, IMRT provided better sparing in all dose ranges with 22.1% reduction in V45 Gy. This pattern was shown to be consistent across the post-op and intact-cervix cases examined. ConclusionsThe goal of this study was to explore techniques that particularly minimized low-dose in PBM, in light of the recent findings that showed association of V10 and V20 Gy with acute hematologic toxicity in patients undergoing concurrent chemotherapy. Due to its physical characteristics (i.e., low entrance dose and Bragg peak) of protons, 3D-CPT showed superior sparing in the low dose range as well as target coverage uniformity. However, IMRT showed favorable sparing of all critical structures at higher doses. Therefore, further studies are warranted to exploit the usefulness of protons for other planning/treatment objectives as well. The goal of this study was to explore techniques that particularly minimized low-dose in PBM, in light of the recent findings that showed association of V10 and V20 Gy with acute hematologic toxicity in patients undergoing concurrent chemotherapy. Due to its physical characteristics (i.e., low entrance dose and Bragg peak) of protons, 3D-CPT showed superior sparing in the low dose range as well as target coverage uniformity. However, IMRT showed favorable sparing of all critical structures at higher doses. Therefore, further studies are warranted to exploit the usefulness of protons for other planning/treatment objectives as well.