Dosimetric comparison between helical tomotherapy, volume modulated arc-therapy and Fixed-Field intensity modulated radiation therapy in postoperative adjuvant radiotherapy for cervical cancer

Abstract

Background: To evaluate the dosimetric parameters among three different radiotherapy techniques in patients with postoperative cervical cancer, including the Helical Tomotherapy (HT), the Volume Modulated Arc-Therapy (VMAT), and the Fixed-Field intensity modulated radiation therapy (FF-IMRT). Methods: Fifteen cervical cancer patients treated with postoperative radiotherapy were re-planning with HT, VMAT and FF-IMRT. The prescribed target dose of the patients was 1.8/45Gy. The paired-samples t-test was used to compare the dosimetric parameters of the planning target and OARs (Organs at risk), and the efficiency of radiation delivery. Results: Compared with the VMAT and FF-IMRT, the HT plans showed significant improvement in the conformity index (CI) and the homogeneity index (HI). In addition, the HT plans also significantly reduced the volume of high-dose region of the OARS, especially in the V30, V40 of small bowel, rectum and bladder. Meantime, the advantage of VMAT is that it reduced the treatment time and improved the efficiency of radiation delivery obviously, compared with the HT (293.8 ± 12.8s Vs. 557.6 ± 51.9s, P < 0.001) and FF-IMRT (293.8 ± 12.8s Vs. 581.8 ± 26.1s, P < 0.001). Conclusion: Our result reveals that HT showed better CI and HI for the target and reduced high dose volumes to OARs compared with VMAT and FF-IMRT, but the lower dose volumes to OARs increased slightly. As for the benefit of VMAT, it demonstrated the shortest treatment time. Our results could provide guidance for selecting the appropriate radiation technologies for cervical cancer patients who undergoing postoperative adjuvant pelvic radiotherapy.

Comparison of volumetric modulated arc therapy and helical tomotherapy for prostate cancer using Pareto fronts

“…Also, our results showing that VMAT can deliver dose in a shorter time than HT is in agreement with the other studies. 10,11,13,15 Furthermore, our finding that plan computation times for VMAT are longer than those for HT is consistent with the literature 48 and is explained because, mathematically speaking, HT is an easier optimization problem than VMAT. 42,43 Finally, a previous study on 3 patients suggested that the distance between Pareto fronts for different treatment techniques was related to the relative PTV-rectum-overlap volume.…”

“…This finding is in agreement with studies that were in favor of VMAT for simple geometries 15,16 and showed that HT was superior for complex geometries. 12,13 The reason why older studies were never in favor of VMAT, even for simple geometries, is the following: 10,11,14,[44][45][46] VMAT is a difficult, non-convex optimization problem that requires sophisticated optimization algorithms to avoid getting trapped in a local optimum far away from the global optimum. 42,43,47 With the development of new algorithms and faster computers, one may expect VMAT to get better over years.This is not the case for HT,because it is an easier convex optimization problem.…”

“…8,9 In the literature, many studies have compared different set-ups, some of which specifically compared VMAT and HT treatment techniques for prostate 10,11 and other cancer sites. 12,13 However, in each case, the studies compared one VMAT and one HT treatment plan, with some dose metrics favoring VMAT and others favoring HT. The decision as to which plan was better thus depended on individual physician preference.…”

“…Studies comparing different setups using the more objective method of Pareto front comparisons are scarcer. [9][10][11][12][13][14] Two studies specifically compared VMAT and HT using Pareto fronts in one prostate 15 and one breast cancer patient. 16 However, to the authors' knowledge, there are no studies comparing VMAT and HT using Pareto fronts for prostate cancer in more than one patient.…”

“…As a Pareto front represents the set of best possible treatment plans for a given set‐up, that is, for a given treatment technique applying given machine parameters, it can be used to make a fair comparison between those set‐ups 8,9 . In the literature, many studies have compared different set‐ups, some of which specifically compared VMAT and HT treatment techniques for prostate 10,11 and other cancer sites 12,13 . However, in each case, the studies compared one VMAT and one HT treatment plan, with some dose metrics favoring VMAT and others favoring HT.…”