The role Of intensity-modulated radiotherapy in the treatment of parotid tumors (original) (raw)
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The Role Of Intensity-Modulated Radiotherapy In the Treatment of Parotid Tumors* 1
International Journal of Radiation …, 2002
Purpose: To compare intensity-modulated radiotherapy (IMRT) treatment plans with three-dimensional conformal radiotherapy (3D-CRT) plans to investigate the suitability of IMRT for the treatment of tumors of the parotid gland. Methods and Materials: One 3D-CRT treatment plan and 10 IMRT treatment plans with differing beam arrangements were produced for each of nine patient data sets. The plans were compared using regret analysis, dose conformity, dose to organs at risk, and uncomplicated tumor control probability (UTCP). Results: The target dose was comparable in the 3D-CRT and IMRT plans, although improvements were seen when seven and nine IMRT fields were used. IMRT reduced the mean dose to the contralateral parotid gland and the maximum doses to the brain and the spinal cord, but increased the ipsilateral lens dose in some cases. Each IMRT arrangement produced a higher UTCP than the 3D-CRT plans; the largest absolute difference was 9.6%. Conclusions: IMRT is a suitable means for treating cancer of the parotid, and a five-field class solution is proposed. It produced substantial sparing of organs at risk and higher UTCPs than 3D-CRT and should enable dose escalation.
Alexandria Journal of Medicine, 2013
Introduction: Postoperative radiotherapy of the parotid gland could be achieved with various radiotherapy techniques. However they irradiate differently the surrounding organs at risk (OARs) in particular the cochlea, oral cavity & contralateral parotid causing significant increase in the risk of oral mucositis, xerostomia, and hearing deficits on the irradiated side. Objectives: The aim of this study was to compare radiation doses received by target volume and different surrounding OARs using three different parotid irradiation techniques aiming to achieve the optimum technique which shows adequate target coverage and sparing of surrounding OARs during postoperative 3DCRT treatment of parotid gland cancer patients. Methodology: Ten patients diagnosed as having parotid cancer were included in this study. They were subjected to CT simulation and scans were transferred to the treatment planning system. Target volumes and contralateral parotid, oral cavity, cochlea, spinal cord, brain stem, eyes, lenses and optic nerves were contoured. Three plans were done using (a) ipsilateral oblique wedged photon
Head and neck intensity modulated radiotherapy parotid glands: time of re-planning
La radiologia medica, 2013
Purpose To investigate the correct time point for replanning by evaluating dosimetric changes in the parotid glands (PGs) during intensity-modulated radiotherapy (IMRT) in head and neck cancer patients. Materials and methods Patients with head and neck cancer treated with IMRT were enrolled. During treatment all patients underwent cone-beam computed tomography (CBCT) scans to verify the set-up. CBCT scans at treatment days 10, 15, 20 and 25 were used to transfer the original plan (CBCT plan I, II, III, IV, respectively) using rigid registration between the two. The PGs were retrospectively contoured and evaluated with the dose-volume histogram. The mean dose, the dose to 50 % of volume, and the percentage of volume receiving 30 and 50 Gy were evaluated for each PG. The Wilcoxon sign ranked test was used to evaluate the effects of dosimetric variations and values \0.05 were taken to be significant. Results From February to June 2011, ten patients were enrolled and five IMRT plans were evaluated for each patient. All the dosimetric parameters increased throughout the treatment course. However, this increase was statistically significant at treatment days 10 and 15 (CBCT plan I, II; p = 0.02, p = 0.03, respectively). Conclusion CBCT is a feasible method to assess the dosimetric changes in the PGs. Our data showed that checking the PG volume and dose could be indicated during the third week of treatment.
Journal of Medical Physics, 2013
For the head-and-neck cancer bilateral irradiation, intensity-modulated radiation therapy (IMRT) is the most reported technique as it enables both target dose coverage and organ-at-risk (OAR) sparing. However, during the last 20 years, three-dimensional conformal radiotherapy (3DCRT) techniques have been introduced, which are tailored to improve the classic shrinking field technique, as regards both planning target volume (PTV) dose conformality and sparing of OAR's, such as parotid glands and spinal cord. In this study, we tested experimentally in a sample of 13 patients, four of these advanced 3DCRT techniques, all using photon beams only and a unique isocentre, namely Bellinzona, Forward-Planned Multisegments (FPMS), ConPas, and field-in-field (FIF) techniques. Statistical analysis of the main dosimetric parameters of PTV and OAR's DVH's as well as of homogeneity and conformity indexes was carried out in order to compare the performance of each technique. The results show that the PTV dose coverage is adequate for all the techniques, with the FPMS techniques providing the highest value for D95%; on the other hand, the best sparing of parotid glands is achieved using the FIF and ConPas techniques, with a mean dose of 26 Gy to parotid glands for a PTV prescription dose of 54 Gy. After taking into account both PTV coverage and parotid sparing, the best global performance was achieved by the FIF technique with results comparable to that of IMRT plans. This technique can be proposed as a valid alternative when IMRT equipment is not available or patient is not suitable for IMRT treatment.
Hospital Practices and Research
Background: Three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) techniques are used for the treatment of patients with laryngeal cancer. Objective: This study aimed to investigate the effects of these 2 treatment techniques on the planning target volume (PTV) (laryngeal cancer), dose homogeneity, dose of organs at risk (OARs) (parotid glands), and conformity index. Methods: This study compared 2 treatment techniques and was conducted from October 2018 to April 2019 at the Zhianawa Cancer Center (ZCC), Sulaimaniyah, Iraq. Eight patients with laryngeal cancer were selected for this study. 3D-CRT and IMRT were used to produce the maximum dose of target volume coverage and minimum dose to the parotid glands. Elekta synergy with a photon beam of 6 MV was used for all measurements. Data analysis was performed using the available statistical package of SPSS 25. Results: The comparison of 3D-CRT with IMRT showed that the mean conformity index value ...
The British Journal of Radiology, 2012
Objectives: This study evaluates the interobserver variation in parotid gland delineation and its impact on intensity-modulated radiotherapy (IMRT) solutions. Methods: The CT volumetric data sets of 10 patients with oropharyngeal squamous cell carcinoma who had been treated with parotid-sparing IMRT were used. Four radiation oncologists and three radiologists delineated the parotid gland that had been spared using IMRT. The dose-volume histogram (DVH) for each study contour was calculated using the IMRT plan actually delivered for that patient. This was compared with the original DVH obtained when the plan was used clinically. Results: 70 study contours were analysed. The mean parotid dose achieved during the actual treatment was within 10% of 24 Gy for all cases. Using the study contours, the mean parotid dose obtained was within 10% of 24 Gy for only 53% of volumes by radiation oncologists and 55% of volumes by radiologists. The parotid DVHs of 46% of the study contours were sufficiently different from those used clinically, such that a different IMRT plan would have been produced. Conclusion: Interobserver variation in parotid gland delineation is significant. Further studies are required to determine ways of improving the interobserver consistency in parotid gland definition.
International Journal of Radiation Oncology*Biology*Physics, 2004
Background and Purpose: The use of intensity-modulated radiotherapy (IMRT) is now widely advocated for the treatment of head-and-neck cancers, to increase the therapeutic ratio of radiotherapy used as sole modality of treatment or in combination with chemotherapy. This report aims to summarize the technical and dosimetric factors to be taken into consideration to assess the respective advantages of the various high conformality treatments in radiotherapy, especially in the framework of quality assurance procedures. Materials and Methods: Twenty-six head-and-neck cancer patients were irradiated following a feasibility internal protocol with IMRT. Treatments were performed with either the static step-and-shoot (20) or the dynamic sliding window (6) techniques on a 6 MV Varian Clinac equipped with a multileaf collimator with 80 leaves. Dose plans were computed using commercial treatment planning systems: MDS-Nordion Helax-TMS for static cases and Varian Eclipse for dynamic cases. Dose plans were evaluated in terms of physical quantities based on dose-volume histograms and isodose distributions. Each IMRT plan was also compared to a reference 3D conformal therapy plan (3DCRT). Results: Elective target volumes ranged from 530 to 1151 cm 3 with a mean of 780 ؎ 141 cm 3 . Boost volumes ranged from 248 to 832 cm 3 with a mean of 537 ؎ 165 cm 3 . Thirty-two dose plans were generated with static technique and 10 with dynamic. In the static mode, 6.8 ؎ 3.4 fields were applied on average with 12.5 ؎ 1.3 segments per field. In the static mode, 264 ؎ 56 MU per Gy were erogated, whereas in the dynamic mode, 387 ؎ 126 MU per Gy were erogated, to be compared to 147 ؎ 20 computed for reference 3DCRT plans. For all target volumes in general, conformity was improved compared to 3DCRT (e.g. V 95 increased from 85% to 93% with p < 0.001, or equivalent uniform dose normalized to prescribed dose increased from 0.86 to 0.96 with p ؍ 0.002). Irradiation of parotid glands or spinal cord improved, as well: For parotids, D 2/3V reduced from 59 Gy to 41 Gy (p < 0.001). For spinal cord, D max reduced from about 40 Gy to about 30 Gy (p < 0.001).
Whole-brain Irradiation Field Design: A Comparison of Parotid Dose
Medical dosimetry : official journal of the American Association of Medical Dosimetrists, 2017
Whole-brain radiation therapy (WBRT) plays an important role in patients with diffusely metastatic intracranial disease. Whether the extent of the radiation field design to C1 or C2 affects parotid dose and risk for developing xerostomia is unknown. The goal of this study is to examine the parotid dose based off of the inferior extent of WBRT field to either C1 or C2. Patients treated with WBRT with either 30 Gy or 37.5 Gy from 2011 to 2014 at a single institution were examined. Parotid dose constraints were compared with Radiation Therapy Oncology Group (RTOG) 0615 nasopharyngeal carcinoma for a 33-fraction treatment: mean <26 Gy, volume constraint at 20 Gy (V20) < 20 cc, and dose at 50% of the parotid volume (D50) < 30 Gy. Biologically effective dose (BED) conversions with an α/β of 3 for normal parotid were performed to compare with 10-fraction and 15-fraction treatments of WBRT. The constraints are as follows: mean < BED 32.83 Gy, V15.76 (for 10-fraction WBRT) or V17...
International Journal of Medical Research and Review, 2019
Introduction: Radiotherapy in head and neck cancers is treated for several weeks and daily setup and reproducibility is a challenge. This daily variability causes setup errors which accounts planning target volume margins. Reduced PTV margins have to be taken to decrease the dose to the parotid glands, without compromising on loco regional control rates. The present study is done to identify setup errors and see the feasibility to decrease the PTV margins by creating dummy radiotherapy plans in order to decrease dose to parotid glands. Material and Methods: 420 portal images were evaluated for setup errors in three dimensions (Antero Posterior, Left to Right and Superior to Inferior) which were performed in ten patients of oropharyngeal squamous cell carcinoma. All patients were treated in supine position using immobilization cast. After target volume delineation a PTV margin of 7 mm was given. Dosimetric parameters of PTV and organs at risk were assessed. PTV margins were calculated according to three methods proposed by Stroom, Van Herk and ICRU 62. Dummy radiotherapy plans were generated using new PTV margins and compared with 7mm PTV margins. The data was analyzed using 3-way ANNOVA test for statistical significance. Results: The optimum PTV margins were 4mm in LR and SI direction and 7mm in AP direction. The PTV parameters (V95, D95, Dmax, Dmean, HI and CI) had no significant difference among different radiotherapy plans with different PTV margins. There was a significant decrease in the dose to right parotid (39.12 Gy to 32.88Gy; p-0.04), left parotid (37.90 to 31.21Gy; p-0.03) and parotid combined (38.65 to 31.45 Gy; p-0.01) when 7mm PTV margins were reduced to 4mm PTV margins. The results of dummy radiotherapy plans using asymmetric PTV margins (LR-4mm, SI-4mm and AP-7mm) and symmetrical PTV margins (4mm in all directions) are compared with PTV margins (7mm in all directions), in terms of PTV and OAR dosimetric parameters. Conclusion: The decreased PTV margins of 4mm decreases the dose to the parotid significantly. The implementation of radiotherapy plans needs to be supplemented by daily IGRT.