|Year : 2021 | Volume
| Issue : 4 | Page : 172-179
Dosimetric comparison of three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and volumetric modulated arc therapy in high-risk prostate cancer
Ozlem Aynaci1, Fatma Çolak1, Lasif Türker Serdar2, Adnan Yöney3
1 Department of Radiation Oncology, Faculty of Medicine, Karadeniz Technical University, Trabzon, Turkey
2 Department of Radiation Oncology, Kanuni Research and Education Hospital, Trabzon, Turkey
3 Department of Radiation Oncology, Onkomer Oncology Center, İzmir, Turkey
|Date of Submission||09-Sep-2021|
|Date of Acceptance||26-Sep-2021|
|Date of Web Publication||09-Dec-2021|
Dr. Ozlem Aynaci
Department of Radiation Oncology, Faculty of Medicine, Karadeniz Technical University, Trabzon
Source of Support: None, Conflict of Interest: None
Purpose: In this study, we aimed to compare the doses of the prostate gland and organs at risk (OAR) using dose volume histograms after external body radiation therapy options, Intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and hybrid three-dimensional conformal radiotherapy (3DCRT), in patients diagnosed with high-risk prostate cancer. Materials and Methods: A total of 14 male patients with high-risk prostate cancer who received prostate radiotherapy combined with elective nodal irradiation, were selected; the total prostate doses were 78 Gy in 39 fractions and pelvic lymph nodes doses were 56 Gy in 28 fractions. The target coverage was evaluated in the PTV with the following parameters: Dmean, Dmin, Dmax, CN, and HI, and each normal tissue was evaluated using percentage volumes of reference doses which were previously defined by Radiation Therapy Oncology Group and QUANTEC criteria. Results: In target volumes, 95% of the targeted dose was adequately covered in all three of the 3BKRT, IMRT, and VMAT techniques. In terms of OAR, the percentages of volume exposed to high doses are much lower in the reverse plan IMRT and VMAT technique compared to the 3DCRT technique. There was no significant superiority between IMRT and VMAT in terms of reference values for rectum, bladder, femoral heads, bulbus penis, and small intestines. Conclusion: The superiority of IMRT and VMAT techniques over 3DCRT techniques has been clearly demonstrated, especially in terms of OAR, in patients with a diagnosis of high-risk prostate cancer. It is thought that one of these two techniques can be preferred by the possibilities in every radiotherapy clinic.
Keywords: Elective nodal irradiation, high risk, intensity-modulated radiotherapy, prostate cancer, three-dimensional conformal radiotherapy, volumetric modulated arc therapy
|How to cite this article:|
Aynaci O, Çolak F, Serdar LT, Yöney A. Dosimetric comparison of three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and volumetric modulated arc therapy in high-risk prostate cancer. J Radiat Cancer Res 2021;12:172-9
|How to cite this URL:|
Aynaci O, Çolak F, Serdar LT, Yöney A. Dosimetric comparison of three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and volumetric modulated arc therapy in high-risk prostate cancer. J Radiat Cancer Res [serial online] 2021 [cited 2022 May 16];12:172-9. Available from: https://www.journalrcr.org/text.asp?2021/12/4/172/332105
| Introduction|| |
Prostate cancer is currently divided into very low, low, intermediate, high, and very high-risk groups according to prostate-specific antigen values, Gleason score values, and pathological stage of the tumor. Treatment options based on risk groups include hormonal therapy (HT), external body radiation therapy (EBRT), brachytherapy (BRT), and radical prostatectomy (RP). In general, follow-up, surgery or EBRT, BRT are preferred in patients in the early stage, low-intermediate risk group. In high-risk patients and locally advanced patients, EBRT is the first choice together with HT.
Radiotherapy applications initially were applied with low-energy X-rays at the beginning of the 20th century, and today, high-energy (megavoltage) X-rays are commonly used with the contributions of the developments in the field of computers and engineering. While EBRT was conventionally planned and treated with two-dimensional techniques in prostate cancer in the 1990s, the transfer of imaging methods obtained with computed tomography (CT) to radiotherapy planning systems allowed the use of three-dimensional methods. With these advances, the relationship of the tumor with normal tissue is more clearly determined. High doses are applied to both target tumor volumes and surrounding normal tissues with conventional treatments. It is possible to protect normal tissues more with three-dimensional conformal radiotherapy (3DCRT and 3BKRT) and intensity-modulated radiation therapy (IMRT) techniques. IMRT is one of the latest innovations brought by technology in radiotherapy. In the IMRT technique, all terms used in 3DCRT such as dose-volume charts (dose volume histograms [DVH]) and target-critical organ definitions are used. Therefore, IMRT can be considered as an extension of 3DCRT. Better dose coverage is obtained, especially in concave-shaped target volumes, as areas with adjusted IMRT dose intensities are used. Most researchers have shown that IMRT is superior to 3DCRT for the head and neck, prostate, and cervical regions.,,,,, By developing volumetric modulated arc therapy (VMAT), another form of IMRT technique, treatments that can rotate 360° around the patient and thus provide more accurate dose distribution can be applied., In this study, we aimed to compare the doses of the target volumes and organs at risk (OAR) at risk (OAR) after 3DCRT, IMRT, and VMAT, which are among the EBRT options, using DVH in patients with a diagnosis of high-risk prostate cancer. It is thought that in the high-risk prostate cancer patient group undergoing elective lymphatic area irradiation, it can provide an idea to choose the most appropriate treatment plan for high dose distribution in target volumes and high protection in surrounding tissues.
| Materials and Methods|| |
A total of 14 consecutively treated patients with high-risk prostate cancer formed the study cohort. All received definitive radiotherapy with prophylactic nodal EBRT.
Fourteen high-risk prostate cancers who received definitive EBRT with prophylactic nodal irradiation were investigated. All patients were treated in our clinic using linear accelerator with 6 MV and 5 mm-multileaf collimator.
Computed tomography scanning for treatment planning
Existing images taken previously with general electric optima CT machine and used in actual treatments of the patients were reloaded into the Treatment Planning System (Eclipse, version 10, Varian Medical Systems) with a DICOM network connection, and the target volumes and OAR were contoured by a single radiation oncologist. In all patients, it was ensured that the bladder was full, and the rectum was empty before imaging. In the imaging, the patients were in the supine position and were scanned with a cross-sectional distance of 2.5 mm, with the upper border of the 4th vertebra and the lower border under the trochanter minor of the femur.
Delineation of target and organs at risk
In high-risk patients, the prostate gland, all seminal vesicle and obturator, proximal external and internal iliac lymph nodes were contoured as CTV-1. PTV-1 was created by adding a safety margin of 1 cm in all directions to the pelvic lymph nodes. The prostate gland seminal vesicles are contoured as CTV-2 and PTV-2 is formed, a safety margin of 1 cm in all directions, except for posteriorly, for which it was 0.6 cm. In the first phase, the PTV-1 pelvic nodes were received and the PTV-2 prostate and seminal vesicles received 56 Gy, both in 28 fractions. In the second phase, the PTV-2 prostate and seminal vesicles boost received 22 Gy in 11 fractions, for a total PTV prostate dose of 78 Gy in 39 fractions. Considering the side effects recorded in randomized studies on prostate cancer radiotherapy, it has been shown that the rectum, bladder, penil bulb, femoral heads, and small intestines are the most affected organs. In this study, we contoured these structures as OAR. The rectum is contoured between the anal verge and the rectosigmoid junction. Target dose limits for OAR are defined according to dose tables established by QUANTEC and Radiation Therapy Oncology Group.
Design of the treatment plans
During IMRT planning, to better coverage, the desired dose, a margin of 0.1 mm is given to each PTV from all directions, and the PTV value, that is, the optimum PTV (OPTV), is created. In all three different planning techniques, it was taken into account that the maximum dose in PTV in 3DCRT and OPTV in IMRT should not exceed 107% and that PTV and all doses were prescribed to a minimum isodose line encompassing ≥95% of the PTV. The percentage values corresponding to the doses received by the critical organs in certain volumes were examined. The target doses and dose-volume limit restrictions for OAR are listed in [Table 1]. Tables have been prepared to analyze the values in these volumes statistically. In addition, DVHs of critical organs were established.
In IMRT treatment planning, nine areas were used for PTV-1 and seven areas were determining equal angle intervals for PTV-2 (angles 0, 40, 80, 120, 160, 200, 240, 280, and 320 for 9 areas; 0 for 7 areas, 51, 102, 153, 204, 255, and 306). 6 MV photon energy was used to reduce the probability of neutron formation. After the areas were determined, the optimization process was started. In the optimization process, it was tried to ensure that the OPTV volume received 95% of the treatment dose and that the critical OAR did not exceed the defined dose values.
Three-dimensional conformal radiotherapy
In the 3DCRT planning, the reciprocal 4-field technique (box technique) was used for PTV-1. To ensure dose homogeneity in required planning, a 5° tilt toward the rectum was given in the opposite side areas (90 and 270 angles). The multi-field technique was used by selecting seven fields for PTV-2. While determining these angles, the angles that minimize the dose of rectum and bladder were chosen. Multi-leaf collimators were used with a 5-mm margin to protect critical organs in each area of all the plans created. The margin of multi-leaf collimators was further reduced in the regions where the rectum and bladder organs are located, and dose reduction was aimed at critical organs. Since the PTV is deeply located, 18 MV photon energy was used.
Volumetric modulated arc therapy
A double arch was used as the treatment area for the VMAT plans. A 365° arc was scanned, with the angles used in arc planning starting from 178° for the first area and ending at 182° counterclockwise. For the second arc area, an arc of 365° was scanned, starting at 182° and ending at 178° clockwise. After the areas were determined, the optimization process was started. It was ensured that the target volumes received 95% of the desired dose and the OAR did not exceed the defined dose values.
Plan comparison and statistical analyses
In a comparison of target volume data in three different treatment planning techniques, Dmean (Gy), Dmax (Gy), Dmin (Gy), CN, and HI data were compared by using DVHs of PTV-1 and PTV-2. When comparing the dose values in OAR; V50 (%), V60 (%), V65 (%), V70 (%) and V75 (%) for the rectum; V65 (%) V70 (%) and V75 (%) for bladder; V30 (%), V40 (%) and V45 (%) for femoral heads; Dmean (Gy) for penil bulb and V45 (cc) for small bowel were chosen.
In the comparison of the plans created with three different treatment planning techniques in terms of the data obtained from the DVHs, the “ANOVA” test was used in the parametric conditions were met (if the data conformed to the normal distribution) and otherwise “KruskalWallis” was used. In the pairwise comparisons of the groups in terms of measurement data, if the parametric conditions are met, the “Bonferroni” test, if not, the “MannWhitney U-test with Bonferroni Correction” was determined.
| Results|| |
Target coverage and doses
CT images of 14 high-risk prostate cancer patients were selected, and 3DCRT, IMRT, and VMAT plans were compared. PTV coverage and doses are shown in [Table 2]. An example of the dose distribution created in three different planning techniques is shown in [Figure 1]. The lowest Dmean (Gy) value was found in the 3DCRT technique for PTV-1 and in the IMRT for PTV-2, while the highest value was found in VMAT planning. When the three techniques were compared, the difference between them was found to be statistically significant for both PTV (P = 0.0001). In the pairwise analyzes performed between the techniques, the Dmean (Gy) value was found to be significantly higher in VMAT plans than in 3DKRT and IMRT plans (P = 0.0001 and P = 0.001).
|Figure 1: Representative three-dimensional conformal radiotherapy (left), intensity modulated therapy (middle), volumetric modulated arc therapy (right) and helical tomotherapy (HT) (right) dose distributions with at least 15 Gy. Nodal and prostate planning target volumes are shown in purple, with isodose lines from 74 Gy|
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|Table 2: Comparison of target coverage metrics for the planning target volume as a function of plan modality|
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In our study, 95% of the targeted dose in PTV-1 and PTV-2 volumes of high-risk prostate cancer patients was adequately wrapped in all three of the 3DCRT, IMRT, and VMAT techniques. Dmin (Gy) value was found in both PTV-1 and PTV-2 with the smallest IMRT technique. When the plans were examined, it was seen that these low-dose regions consisted of very small volumes close to the OAR. The Dmax (Gy) and the Dmean (Gy value was found the highest in VMAT technique in both PTV-1 and PTV-2 [Table 2].
The mean CN-1 values are 0.54 in the 3DCRT technique, 0.84 in the IMRT technique, and 0.78 in the VMAT technique; the mean CN-2 values were 0.51 in the 3DCRT technique, 0.76 in the IMRT technique, and 0.68 in the VMAT technique. The difference between the three techniques was statistically significant (P = 0.0001). In terms of CN-1 and CN-2, the smallest value was found in the 3DCRT technique, whereas the highest value was found in the IMRT technique) [Table 2].
The HI-1 mean values are 0.08 in the 3DCRT technique, 0.07 in the IMRT technique, and 0.07 in the VMAT technique; the HI-2 mean values are 0.06 in the 3DCRT technique, 0.06 in the IMRT technique, and 0.09 in the VMAT. When the three techniques were compared in terms of HI-1 and HI-2 values, the difference between them was found to be statistically significant (P = 0.031 and P = 0.0001), respectively. While no significant difference was observed between the three techniques in the paired analyzes in HI-1, the HI-2 value was found to be significantly higher in the VMAT technique than in the 3DCRT and IMRT techniques (P = 0.001 and P = 0.0001).
While there was no significant difference between IMRT and VMAT techniques in terms of conformity in PTV-1, it was observed that more ideal conformality was achieved in planning made with the IMRT technique in PTV-2. In the high-risk group, the volume of PTV-1 is quite large compared to PTV-2. There was no significant difference between the two techniques, even when the volume was large. In terms of homogeneity, there was no significant difference between them in PTV-1. In PTV-2, as in the mean risk group, statistically significantly higher homogeneity index values were found in the IMRT technique compared to the VMAT technique.
The mean values of MU were 474 in the 3DCRT technique, 2650 in the IMRT technique, and 1393 in the VMAT technique. The highest value was seen in the IMRT technique and the lowest in the 3DCRT technique. A statistically significant difference was found between the techniques in the analysis (P = 0.0001). The mean value of MU in the 3DCRT technique was significantly smaller (P = 0.001 and P = 0.0001) when compared with other techniques in pairs; when IMRT and VMAT techniques were compared in pairs, it was found to be significantly larger in the IMRT technique (P = 0.0001; [Table 2]].
Normal tissue irradiation
The dose-volume results and statistical comparison of all three plans in terms of OAR are presented in [Table 3]. A significant difference was found between the techniques in terms of the doses received by all reference volumes determined for the rectum (P = 0.0001). In the double analyzes made for V50 (%), V60 (%), V65 (%), and V70 (%) values, the doses obtained in the 3DCRT technique were found to be significantly higher than the other techniques. In addition, although it was observed that the doses in the VMAT technique were slightly smaller than the IMRT technique in values other than the V75 (%) value, no statistically significant difference was observed (P = 0.187, P = 1.000, P = 1.000, P = 0.935, and P = 0.993).
|Table 3: Comparison of organs at risk dose-volume metrics as a function of plan modality|
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When the three techniques were compared in terms of V65 (%), V70 (%), and V75 (%) values, the difference between them was found to be statistically significant (P = 0.027, P = 0.007, and P = 0.023). For all reference volumes, no significant difference was observed in the bilateral statistical analyzes between 3DCRT, IMRT, and VMAT techniques. 3DCRT technique had the higher the volumes receiving 45 Gy doses than IMRT and VMAT techniques (P = 0.008 and P = 0.013) in the paired analyzes. There was no significant difference between IMRT and VMAT techniques (P = 1.000).
In the IMRT and VMAT techniques, which were reversed in terms of OAR, the percentages of volume exposed to high doses compared to the 3DCRT technique were found to be statistically significantly lower. No significant superiority could be established between IMRT and VMAT techniques in terms of reference values for the rectum, bladder, femoral heads, penil bulb, and small intestines. The reason for this is thought to be because this process was not managed by the same medical physicist, although the dose limitations in the optimization process were kept the same for both plan techniques. In addition, it has been observed that the near-ideal selection of the angles and number of areas used in the IMRT technique and the adjustments during optimization with small steps improved the results obtained at the target volumes. It is thought that by increasing the number of images participating in the study, some values can be changed in favor of one of the techniques in terms of statistical significance. It is estimated that increasing the number of arcs in the planning made with the VMAT technique will improve the results in terms of the target volume and the doses taken by the OAR.
| Discussion|| |
New techniques have been developed in the field of radiotherapy since the 1st day of EBRT to deliver the maximum possible dose to the target volume and to protect the healthy tissues close to the target volume. When these new technologies reached acceptable clinical endpoints as a result of the applications on a sufficient number of patients, they are accepted in the field of radiotherapy application. Tumor control, toxicity rates, survival rates, and quality of life outcomes were considered when examining the clinical utility of these innovations. These criteria constitute the main rationale of 3DCRT, IMRT, and VMAT, which came to the fore after conventional treatments. There are two important points to consider when applying these techniques: First, it is important to pay attention to the movements in the treatment area (reason for creating IM) and setup errors (reason for creating SM) and to ensure that the planned dose is applied equally. Otherwise, it will not be possible to achieve the treatment gain target, which is aimed to be achieved above, and possible to cause greater absolute errors than we thought may occur in treatment methods with this sharp dose change. The aim of our study was determined to compare 3DCRT, IMRT, and VMAT techniques by using parameters that determine tumor control and doses that may cause toxicity in critical organs.
In the IMRT technique, radiation is divided into even more angles to provide a more conformal dose distribution. Different intensities of radiation can be applied at each angle. Thus, a more conformal area can be created in tumors with a more concave shape and the OAR can be preserved better. On the other hand, it is known that more complex mechanisms such as treatment planning and quality control systems are required and there may be imobilization problems during treatment because of longer irradiation. The increase in MU also increases the possibility of secondary cancer due to radiation, since it also increases the low dose distributions on the body.
The use of certain fixed angles in the IMRT technique has brought rotational treatments in radiation treatments over time. Tomotherapy and VMAT are two known forms of arch-based rotational therapy. The use of certain fixed angles in the IMRT technique has brought rotational treatments to the agenda over time. Thus, treatment can be applied throughout 360°. Tomotherapy and VMAT are two known forms of arch-based rotational therapy. Palma et al. selected 10 patients with a diagnosis of localized prostate cancer who had previously undergone radical prostate EBRT for the study. CT images were taken with an empty bladder of patients specific to this study. The prostate gland is contoured as CTV. PTV was created with a safety margin of 0.7 cm in all directions and 0.5 cm in the posterior rectum. The radiation dose is 2 Gy/fk with a total of 74 Gy. For comparison, 3DCRT, 5-field IMRT, constant dose rate (cdr) VMAT, variable dose rate (vdr) VMAT techniques were applied. CI, HI, Dmax (Gy), and Dmean values were used in target volume (PTV) evaluation, and rectum, bladder, and femoral heads were determined as critical organs. In addition, MU values are also included in the comparison. For rectum, V20 (%), V40 (%), V70 (%); for bladder V20 (%), V40 (%); V40 (%) values were checked for femoral heads. As a result of the study, it was emphasized that the protection of OAR and the wrapping of PTV at the desired level provide a significant advantage in IMRT and VMAT planning compared to 3DKRT plans. The smallest OAR doses were obtained in the vdr-VMAT technique. At the same time, it was observed that 42% less MU was applied in this technique compared to the IMRT technique. In our study, MU values were found to be significantly lower in the VMAT than IMRT (P = 0.0001).
In terms of covering the PTV, the evaluated CN values were slightly larger (closer to 1) in the IMRT technique and although not statistically significant, it was seen that the PTV covered better than the VMAT technique. In homogeneity assessments, it was observed that the VMAT technique was more successful. In terms of OAR, the results were found to be similar in IMRT and VMAT techniques. In the vdr-VMAT technique, the rectum and femoral head doses are from IMRT; rectum and bladder doses are significantly lower than cdr-VMAT. In the vdr-VMAT technique, the mean MU was 454, significantly (P = 0.005) 42% less than IMRT, and 8% less than cdr-VMAT without statistical significance (P = 0.06). According to this study, the high number of MU can theoretically be held responsible for an increase in the duration of treatment and an increase in the risk of malignancy secondary to treatment, although it has not been fully proven; however, since the volume of normal tissue exposed to low-dose radiotherapy in the treated area is also implicated in the etiology of secondary malignancy, the 3DCRT technique is not completely eliminated in this respect.
In the study conducted by Sale and Moloney, eight patients underwent RP with the diagnosis of localized prostate cancer, followed by EBRT of 75.6 Gy with a total of 1.8 Gy/42 fk were included. As CTV, prostate gland + proximal seminal vesicles in the intermediate-risk group; in the high-risk group, the prostate gland + seminal vesicles were contoured. PTV was created with safety of 1 cm in all directions and 0.5–0.6 cm in the rear. A total of 32 plans were compared using the advanced planning 3DCT technique, static IMRT, single arc VMAT, and double-arc VMAT techniques. Dmax (Gy), Dmin (Gy), Dmean (Gy), D95, and D5 were investigated in PTV. Dmax (Gy) value was found to be statistically significantly higher in single arc VMAT and 3DCRT planning compared to other techniques (P = 0.03 and P = 0.00, respectively). There was no significant difference between the techniques in terms of Dmin (Gy) Dmean (Gy), D95 and D5 (0.49, 0.07, 0.76, and 0.20, respectively) since the number of plans included in the evaluation was insufficient. In our study, Dmin (Gy) value was found to be significantly lower in the IMRT technique in both risk groups.
In another study conducted at Mary Bird Perkins Cancer Center in the USA, single arc VMAT, 7-field IMRT, and 9-field IMRT techniques were compared in 10 patients with locally advanced prostate cancer. An endorectal balloon was applied to all patients. Seminal vesicle invasion was present in five patients and this group, seminal vesicle + prostate was defined as PTV-2, and prostate localization was defined as PTV1. Five patients had lymph node metastases and their pelvic lymph nodes were included in PTV-2. As in the previous study, rectum, bladder, and femoral heads were selected as OARs.
When compared in terms of target volume data (D98, HI, CI) and OAR data, the three techniques were not found to be significantly different from each other. MU and treatment durations were found to be statistically significantly lower with VMAT plans. In the study, the authors attributed the fact that the results were not significantly different from each other: They emphasized that the comparison was not very healthy, since the plans whose results were evaluated belong to daily practices and many radiation oncologists and medical physicists make plans. At the same time, they suggested that the most ideal planning criteria for each technique should have been determined and the plans should have been compared. It was thought that the lack of a standard between treatment volumes and doses affected the results.
In another study conducted by Quan et al. at MD Anderson Cancer Center, plans made with IMRT and VMAT techniques in 11 randomly selected patients with prostate cancer were compared. Prostate + PSV in eight patients and prostate + whole seminal vesicle in 3 patients were defined as CTV. PTV was created by giving a safety margin of 0.7 cm in all directions and 0.5 cm in the rear. The radiation dose is 2 Gy/fk with a total of 76 Gy. Rectum, bladder, and femoral heads were evaluated as OAR. While two arcs were used while preparing VMAT planning, 8, 12, 16, 20, and 26 angled plans were created for each patient in IMRT planning. In a comparison of plans, CN, HI for PTV; Bladder and rectal volumes within 30-, 40-, 50-, and 70-Gy isodose curves and mean doses of these organs were examined for OAR. MUs were also compared to evaluate the irradiation time in each plane. In terms of coverage of PTV, CN and HI values were found to be similar in IMRT and VMAT plans. Rectal doses were found to be significantly lower in the VMAT technique than in the 8-angle IMRT technique; however, the results were similar in cases where angles above 8 were used. Although femoral head doses were higher in VMAT and 24-angle IMRT techniques, they were within dose limitations. MU values increased as the angles increased in IMRT planning. It has been shown that while MU values in VMAT technique were 30% more than the 8-angle IMRT technique and 4% more than 24-angle IMRT. Since 9-angle IMRT was planned in our study, the results obtained with IMRT and VMAT techniques were found to be similar. In terms of bladder doses, there was no significant difference between the plans as in our study.
To compare IMRT and VMAT techniques, 10 patients who received prostate radiotherapy at Illawarra Cancer Center were selected by Hardcastle Nicholas et al. Seminal vesicles were not included as CTV, and only the prostate gland was determined. While creating the PTV, 7 mm safety was given to the CTV. The defined dose was determined as 78 Gy in 39 fractions. D95, V95% and mean dose values were used when comparing PTVs, and DVH plots were used when comparing OAR doses. According to the results, the doses were found to be similar in terms of PTVs, and only D95 (Gy) was found to be slightly lower in the VMAT technique (P = 0.005). Of the rectal doses, V25 (%) was significantly lower in the VMAT technique (P < 0.01), while the V70 (%) value was found to be lower in the IMRT technique (P < 0.01). Considering the doses taken by the femoral heads, higher doses were seen in the VMAT technique. Asymmetrically, it was observed that the dose received by the left femoral head was higher than the right femoral head.
| Conclusion|| |
The superiority of IMRT and VMAT techniques over 3DCRT techniques has been clearly demonstrated, especially in terms of OAR, in patients with a diagnosis of high-risk prostate cancer. It is thought that in each clinic where radiotherapy is applied, one of these two techniques can be preferred in line with its possibilities. Considering that the most statistically significant difference between IMRT and VMAT techniques is in terms of MU values in favor of the VMAT technique, it is recommended to prefer the VMAT technique if clinical conditions are also present.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]