Volumetric Modulated Arc Technique Research Articles

Radiobiological analysis of VMAT treatment plan with flattened and flattening filter free photon beam: an EUD and TCP based comparative study.

This study aimed to evaluate the dosimetric and radiobiological differences between 6MV flattened filter (FF) and flattening filter free (FFF) using volumetric modulated arc (VMAT) technique for head and neck (H&N) cancer patients. Fifteen patients with H&N carcinoma were selected and treated with VMAT with FF (VMATFF) treatment plan. Retrospectively, additional VMAT treatment plans were developed using FFF beams (VMATFFF). Radiobiological parameters, such as equivalent uniform dose (EUD), tumor cure probability (TCP), and normal tissue complication probability (NTCP), were calculated using Niemierko's model for both VMATFF and VMATFFF. Correlation between dosimetric and radiobiological data were analyzed and compared. The conformity index (CI) was 0.975 ± 0.014 (VMATFF) and 0.964 ± 0. 019 (VMATFFF) with p ≥ 0.05. Statistically, there was an insignificant difference in the planning target volume (PTV) results for TCP (%) values, with values of 81.20 ± 0.88% (VMATFF) and 81.01 ± 0.92 (%) (VMATFF). Similarly, there was an insignificant difference in the EUD (Gy) values, which were 71.53 ± 0.33 Gy (VMATFF) and 71.46 ± 0.34 Gy (VMATFFF). The NTCP values for the spinal cord, left parotid, and right parotid were 6.54 × 10-07%, 8.04%, and 7.69%, respectively, in the case of VMATFF. For VMATFFF, the corresponding NTCP values for the spinal cord, parotids left, and parotid right were 3.09 × 10-07%, 6.57%, and 6.73%, respectively. The EUD and Mean Dose to PTV were strongly correlated for VMATFFF. An increased mean dose to the PTV and greater TCP were reported for the VMATFF, which can enhance the delivery of the therapeutic dose to the target.

CNN-based multi-modal radiomics analysis of pseudo-CT utilization in MRI-only brain stereotactic radiotherapy: a feasibility study

BackgroundPseudo-computed tomography (pCT) quality is a crucial issue in magnetic resonance image (MRI)-only brain stereotactic radiotherapy (SRT), so this study systematically evaluated it from the multi-modal radiomics perspective.Methods34 cases (< 30 cm³) were retrospectively included (2021.9-2022.10). For each case, both CT and MRI scans were performed at simulation, and pCT was generated by a convolutional neural network (CNN) from planning MRI. Conformal arc or volumetric modulated arc technique was used to optimize the dose distribution. The SRT dose was compared between pCT and planning CT with dose volume histogram (DVH) metrics and gamma index. Wilcoxon test and Spearman analysis were used to identify key factors associated with dose deviations. Additionally, original image features were extracted for radiomic analysis. Tumor control probability (TCP) and normal tissue complication probability (NTCP) were employed for efficacy evaluation.ResultsThere was no significant difference between pCT and planning CT except for radiomics. The mean value of Hounsfield unit of the planning CT was slightly higher than that of pCT. The Gadolinium-based agents in planning MRI could increase DVH metrics deviation slightly. The median local gamma passing rates (1%/1 mm) between planning CTs and pCTs (non-contrast) was 92.6% (range 63.5–99.6%). Also, differences were observed in more than 85% of original radiomic features. The mean absolute deviation in TCP was 0.03%, and the NTCP difference was below 0.02%, except for the normal brain, which had a 0.16% difference. In addition, the number of SRT fractions and lesions, and lesion morphology could influence dose deviation.ConclusionsThis is the first multi-modal radiomics analysis of CNN-based pCT from planning MRI for SRT of small brain lesions, covering dosiomics and radiomics. The findings suggest the potential of pCT in SRT plan design and efficacy prediction, but caution needs to be taken for radiomic analysis.

Plasmacytoma of nasopharynx - A rare case presentation treated with volumetric modulated arc technique radiotherapy

Extramedullary plasmacytomas (EMPs) are solitary plasma cell neoplasms that involve sites other than bone or bone marrow. It constitutes only 0.4% of tumors of head-and-neck region. Surgery and radiotherapy are standard treatment, depending on the site. Radiotherapy promises 90–100% local control rate and prolonged survival. Here, we are reporting a case of plasmacytoma nasopharynx treated with volumetric-modulated arc technique (VMAT) radiotherapy, with contouring details, dose to target, and nearby structures. Patient had complete response and is relapse free for the past 3 years with minimal toxicity. In our case, the lesion is in nasopharynx and is about 1cm, as such it required precise radiotherapy technique like VMAT, to give targeted dose delivery and sparing the nearby critical organs.

Primary rhabdomyosarcoma of the breast in an adult: A role of volumetric modulated arc technique radiotherapy

Rhabdomyosarcoma (RMS) is the most common soft tissue tumor in children and is rarely seen in adults. It is slightly more common in females. It constitutes <1% of all breast malignancies. Radiologically, it is difficult to differentiate RMS from other breast benign or malignant tumors. Hence, it is often diagnosed late. Immunohistochemistry staining with actin, desmin, myogenin, and myoD1 confirms the diagnosis. There is no standard treatment due to rarity of cases. Role of radiotherapy is still controversial, but many studies have shown the benefit of radiotherapy in large tumors of more than 5 cm. RMSs are usually aggressive tumors with survival ranging from 3 months to 7 years. Here, we report a case of primary RMS of the breast in a 49-year-old female, describing radiological and pathological features and treatment with volumetric modulated arc technique radiotherapy.

A rare case of mantle cell lymphoma of nasopharynx and larynx with synchronous presentation treated with volumetric modulated arc technique radiotherapy

Mantle cell lymphoma (MCL) or mature peripheral B-cell lymphoid neoplasm is a type of non-Hodgkin's lymphoma. It is more common in elderly males. It is very rare, accounting for less than 1% of head and neck malignancies. MCL is usually positive for CD20, CD5, CD43, cyclin D1 and negative for CD10, CD23, and BCL6. It is a very aggressive neoplasm, and hence, patients often present in advanced stage. Due to its rare incidence and short clinical course, there are limited data on standard treatment protocols. Even with the present treatment protocols, only 30% of patients achieve complete response. Here, we present a case of synchronous presentation of MCL of the nasopharynx and larynx in a 69-year-old male. We aim to discuss the investigations and treatment done with volumetric modulated arc technique radiotherapy that led to complete response.

Reirradiation of Locally Recurrent Prostate Cancer with Cyberknife® System or Volumetric Modulated Arc Therapy (VMAT) and IGRT-Clarity®: Outcomes, Toxicities and Dosimetric Evaluation.

Simple SummaryFrom April 2017 to December 2020, 29 patients with prostate cancer recurrence were selected. They received Cyberknife® (CK) treatment (17 pts) or alternatively VMAT (Volumetric Modulated Arc Technique) therapy by IGRT (Image-Guided Radiation Therapy)/Clarity® (12 pts). Urinary (GU), rectal (GI) toxicities, and biochemical control were investigated. Further, the two techniques were dosimetrically compared by rival plans. The VMAT-IGRT Clarity® treatments were replanned applying a template developed for prostate VMAT-SBRT in FFF mode, keeping the same dose/fractionation scheduled for the CK Group (30 Gy in 5 fx at 80% isodose). In the CK group, 23% of patients experienced grade 2 acute GU, while 6% showed grade 2 acute GI. In the VMAT-Clarity® group, 17% of patients showed acute GU toxicity, while for 8% grade 2 late toxicity was recorded. The dosimetric analysis shows that VMAT-FFF allows to deliver a biological equivalent dose to CK, with the advantage of reducing the likelihood of toxicities arising.The management of prostate cancer recurrence following external beam radiotherapy is not defined yet. Stereotaxic body reirradiation therapy showed encouraging results for local and biochemical control. From April 2017 to December 2020, 29 patients with prostate cancer recurrence were collected, joining the retrospective studies CyPro (prot. 46/19 OSS) and CLARO (Prot. 19/20 OSS) trials. Patients received Cyberknife® treatment (17 pts) or alternatively VMAT (Volumetric Modulated Arc Technique) therapy by IGRT (Image-Guided Radiation Therapy)/Clarity® (12 pts). By comparing the reirradiation of two groups, urinary (GU), rectal (GI) toxicities, and biochemical control were investigated. Further, the two techniques were dosimetrically compared by rival plans. The VMAT-IGRT Clarity® treatments were replanned with an optimized template developed for prostate VMAT-SBRT in FFF mode keeping the same dose and fractionation scheduled for Cyberknife Group (30 Gy in 5 fx, at 80% isodose). In the CK group, 23% of patients experienced grade 2 acute GU, while 6% grade 2 acute GI. In the VMAT-Clarity® group, acute GU toxicity was recorded in 17%, while for 8% grade 2 late toxicity was recorded. The dosimetric analysis shows that the VMAT-FFF allows to deliver a biological equivalent dose to CK, with the advantage of reducing the likelihood of toxicities arising.

Accelerated hypofractionated breast radiotherapy with simultaneous integrated boost: a feasibility study.

PurposeTo assess the feasibility of accelerated hypofractionated radiotherapy with simultaneous integrated boost (SIB) in patients with breast cancer.Materials and MethodsA total of 27 patients after breast-conserving surgery were included in this study. Patients were planned on a four-dimensional computerized tomogram, and contouring was done using RTOG guidelines. The dose was 34 Gy/10#/2 week to the breast and 40 Gy/10#/2 week to the tumor bed as SIB with volumetric modulated arc technique. The primary endpoint was grade 2 acute skin toxicity. Doses to the organs-at-risk were calculated. Toxicities and cosmesis were assessed using RTOG/LENT/SOMA and HARVARD/NSABP/RTOG grading scales, respectively. Disease-free survival (DFS) and overall survival (OS) were calculated with Kaplan-Meier curves.ResultsThe mean age of the patients was 42 years. Left and right breast cancers were seen in 17 (63%) and 10 (37%) patients, respectively. The mean values of ipsilateral lung V16 and contralateral lung V5 were 16.01% and 3.74%, respectively. The mean heart doses from the left and right breast were 7.25 Gy and 4.37 Gy, respectively. The mean doses to the contralateral breast, oesophagus, and Dmax to brachial plexus were 2.64 Gy, 3.69 Gy, and 26.95 Gy, respectively. The mean value of thyroid V25 was 19.69%. Grade 1 and 2 acute skin toxicities were observed in 9 (33%) and 5 (18.5%) patients, respectively. Grade 2 hyperpigmentation, edema, and induration were observed in 1 (3.7%), 2 (7.4%), and 4 (14.8%) patients, respectively. Mild breast pain and arm/shoulder discomfort were reported by 1 (3.4%) patient. The median follow-up was 51 months (range, 12 to 61 months). At four years, breast induration, edema, and fibrosis were observed in 1 (3.7%) patient. Cosmesis was excellent and good in 21 (78%) and 6 (22%) patients, respectively. Local recurrence and distant metastases occurred in 1 (3.7%) and 2 (7.4%) patients, respectively. DFS and OS at four years were 88% and 92%, respectively.ConclusionWith this radiotherapy schedule, acute and late toxicity rates were acceptable with no adverse cosmesis. Local control, DFS, and OS were good.

The Effect of Using the Intermediate Dose Calculation Module on Volumetric Modulated Arc Technique Plan Quality in Esophagus Cancer

The Effect of Using the Intermediate Dose Calculation Module on Volumetric Modulated Arc Technique Plan Quality in Esophagus Cancer

Volumetric modulated arc technique radiotherapy in synchronous locally advanced rectal and very high-risk prostate cancer

Volumetric modulated arc technique radiotherapy in synchronous locally advanced rectal and very high-risk prostate cancer

Effect of contrast medium on treatment modalities planned with different photon beam energies: a planning study.

Routinely, patient's planning scans are acquired after administration of iodinized contrast media but they will be treated in the absence of that. Similarly, high energy photons have a better penetrating power, while low energy photons will result in tighter dose distribution and negligible neutron contamination. The aim of the study was to investigate a suitable photon beam energy in the presence of intravenous contrast medium. An indigenously made original-contrast (OC) phantom was mentioned as virtual-contrast (VC) and virtual-without-contrast (VWC) phantom were generated by assigning the Hounsfield Units (HU) to different structures. Intensity-modulated (IMRT) and volumetric-modulated-arc (VMAT) plans were generated as per criteria of the TG-119 protocol. It was observed that the maximum dose to the spinal cord was better with 6 mega-voltage (MV) in IMRT. The coverage of Prostate PTV (PR PTV) was similar with all the photon energies and was comparable with TG-119, except for original-contrast (OC) phantom using the VMAT technique. Homogeneity-index (HI) was comparatively better for VMAT plans. The contrast CT images lower the dose to targets. IMRT or VMAT plans, generated on such CT images will be delivered with higher doses than evaluated. However, the overdose remains non-significant.

Comparison of Hyperfractionated Radiotherapy with Concomitant Chemotherapy and Conventional Chemoradiotherapy in Locally Advanced Head and Neck Cancer Treated with Volumetric Modulated Arc Technique (VMAT)

Comparison of Hyperfractionated Radiotherapy with Concomitant Chemotherapy and Conventional Chemoradiotherapy in Locally Advanced Head and Neck Cancer Treated with Volumetric Modulated Arc Technique (VMAT)

Long-term disease outcome and volume-based decision strategy in a large cohort of multiple brain metastases treated with a mono-isocentric linac-based Stereotactic Radiosurgery technique.

Radiosurgery (SRS) is an effective treatment option for brain metastases (BMs). Long-term results of the first worldwide experience with a mono-isocentric, non-coplanar, linac-based stereotactic technique in the treatment of multiple BMs are reported. patients with multiple BMs, life expectancy > 3months, and good performance status (≤ 2) were treated with simultaneous SRS with volumetric modulated arc technique. Data were retrospectively evaluated. 172 patients accounting for 1079 BMs were treated at our institution from 2017 to 2020. The median number of treated metastases was 4 (range 2-22). Primary tumor histology was: lung (44.8%), breast (32%), and melanoma (9.4%). The 2-year LPFS was 71.6%, respectively. A biological effective dose (BED) ≥ 51.3 Gy10 correlated with higher local control. Uncontrolled systemic disease and melanoma histology were independent prognostic factors correlated with decreased iPFS. Patients with > 10 BMs had a trend towards shorter iPFS (p = 0.055). 31 patients received multiple SRS courses (2-7) in case of intracranial progression. The median iOS was 22.4months. Brainstem metastases and total PTV > 7.1cc correlated with shorter iOS. The 1- and 2-year WBRT-free survival was 83.2% and 61.1%, respectively. Long-term results in a large patient population treated with a mono-isocentric, dedicated technique demonstrated its effectiveness and safety also in the case of multiple courses. The shortened treatment time and the possibility to safely spare healthy brain tissue allows the safe treatment of patients with a large number of metastases and to deliver multiple courses of SRS. In selected cases, the administration of WBRT can be delayed.

Tumor volume as a prognostic factor on the median survival in locally advanced oral cancer treated with definitive chemoradiotherapy.

Surgery has been the mainstay treatment for oral cancer. Those patients, who do not receive surgery are generally treated with concurrent chemoradiotherapy (CCRT). Many factors play a role in patients' survival; tumor volume might be one of those factors. This study aims to determine the effect of the pretreatment tumor volume on the survival of oral cancer. Retrospective study of patients with histological confirmed squamous cell carcinoma, stage III-IV oral cancer, who received definitive CCRT. Tumor volume from pretreatment computed tomography (CT) scans were reviewed and analyzed. The optimal cut-off tumor volume was evaluated by receiver operating characteristic (ROC) curve analysis. From 67 patients, half of the primary tumor sites were oral tongue. The median total tumor volume (TTV) was 73.25 cm3, while the median survival was 12.5 months (95% CI 10.9-20.3). The optimal cut-off TTV =52.9 cm3 (P < 0.0001). The median survival of the patients, who had tumor volume <52.9 cm3 were 34.4 months, and for tumor volume =52.9 cm3 were 8.6 months (P < 0.0001). Multivariate analysis showed that TTV =52.9 cm3, and intensity-modulated radiotherapy (IMRT) or volumetric modulated arc (VMAT) technique had significantly influenced on the overall survival. TTV had an influence on the overall survival of locally advanced oral cancer. In addition, TTV may be considered as a factor in selecting the appropriate treatment option for these patients.

The Use of Interstitial Spacer to Improve Therapeutic Ratio in Stereotactic Radiation Therapy for Retroperitoneal Oligometastasis

Perirectal interstitial hydrogel spacer (HS) is frequently used as a safe and effective method of limiting rectal dose in prostate cancer radiation therapy (RT). There are limited reports in the literature of its use outside the pelvis and no reports of its use for Stereotactic Body Radiation Therapy (SBRT) for abdominal oligometastases. We present a case involving a novel indication for the use of HS: to separate bowel from the high dose region in a patient receiving SBRT for a retroperitoneal oligometastasis from metastatic gastric adenocarcinoma. Using an aseptic technique, 5ml of 1% lignocaine was infiltrated subcutaneously. Under light intravenous sedation and CT guidance, a Chiba needle was used to access the space between the left retroperitoneal mass and adjacent bowel loops. Subsequently 50ml of normal saline was injected to achieve hydro-dissection of the tissue plane to create an anatomical space that was filled by 22ml of HS. Radiation therapy (RT) plans were prepared for pre-spacer and post-spacer anatomy. The prescription was for 40Gy/5# to be delivered using a volumetric modulated-arc technique (VMAT). Treatment planning and dose calculation was performed in Monaco version 5.11. Pre-and post-spacer RT simulation computed tomographies (CTs) demonstrated visibly appreciable separation of bowel loops lateral to the tumor mass (Figure – not shown in abstract). Dose-volume histogram parameters demonstrated a reduction in large bowel maximum dose (Dmax 44.8 Gy vs 35.8 Gy) and volume receiving ≥25Gy (28.3cc vs 18.2cc), exceeding and then meeting departmental tolerances on the pre- and post-spacer plans respectively. There was tumor progression between planning CTs - the pre-spacer planning target volume (PTV) was 300cc, the post-spacer PTV was 333cc. Thus, PTV dosimetry did not improve due to contact with bowel on the medial aspect of the tumor.Tabled 1Abstract 2624; TableTargetOrgans at RiskPTVCTVLarge BowelKidneySpinal CordSmall BowelD98D50D2DmeanD98D50D2DmeanDmaxV25 (cc)DmaxV23 (%)DmaxV23 (cc)DmaxV19.5 (cc)Pre-Spacer35.347.651.245.943.749.251.448.844.828.344.926.513.9034.917.0Post Spacer31.847.450.745.637.649.250.848.235.818.244.825.816.2033.630.5 Open table in a new tab In this case, HS was successful in separating adjacent bowel from the planning target volume and improving large bowel RT dosimetric parameters. HS insertion in the retroperitoneum is feasible and has the potential to improve the therapeutic ratio in appropriately selected patients where PTV dose is limited by an adjacent organ.

Dosimetric comparison of incidental axillary irradiation between three-dimensional conformal and volumetric modulated arc techniques for breast cancer.

Radiotherapy techniques for breast cancer have evolved with efforts to reduce treatment-related side effects. In the present study, we conducted dosimetric analysis of incidental axillary irradiation between volumetric modulated arc therapy (VMAT) and three-dimensional conformal radiotherapy (3D-CRT). A total of 20 patients with early stage left breast cancer who underwent breast-conserving surgery followed by postoperative radiotherapy were analyzed. For VMAT plans, dose-volume constraints were not imposed on the axilla, as with 3D-CRT. We compared the dosimetric parameters of the planning target volumes, organs at risk and axillary level I-III of the two plans. VMAT showed better target coverage and a normal organ-sparing effect compared with 3D-CRT. The incidental axillary irradiation of VMAT was lower; the mean dose and the V40Gy were significantly reduced at all axillary levels, with the exception of no difference in the maximum dose to axillary level I. In conclusion, VMAT decreased incidental axillary irradiation, even in the absence of a dose-volume constraint on the axilla, and can, therefore, decrease the risk of radiotherapy-related lymphedema. However, caution is also required because it is unclear whether this incidental axillary irradiation is beneficial for reducing recurrence on the axilla.

Optimized Volumetric Modulated Arc Technique for Noninvasive Cardiac Ablation to Treat Ventricular Tachycardia

Recent publications (Cuculich et al., NEJM-2017, Robinson et al., Circulation-2019) have shown promising outcomes of radioablation using a single-fraction SBRT to treat patients with refractory, life-threatening, VT. This prompted growing interest across the world to use SBRT to treat VT. The primary goal of this study is to explore an alternative VMAT planning technique to achieve greater Non-Target Heart-Tissue (NTHT) sparing while simultaneously allowing for breath hold (BH) treatments. 13 patients were selected who previously received a single fraction dose of 35 Gy to ITV and 25 Gy to PTV utilizing 3 non-coplanar VMAT arcs of 6 MV photon beams using HD-MLC on a radiosurgery-optimized linac. To further improve NTHT sparing we retrospectively re-planned each patient using 10 ipsi-lateral arcs with optimal gantry, couch and collimator angles. Two plans were generated using 6X FFF and 10X FFF beams with dynamic jaw-tracking. Gantry arc lengths were limited to 90° (< 15s/arc) for feasibility of a potential BH treatments. Couch angles were limited to ± 15° to avoid collisions. Plans were optimized to maximize the NTHT sparing while meeting the protocol constraints for the stomach, esophagus and colon (OAR). Plan quality metrics for both clinical and reoptimized plans are summarized in Table 1. Revised plans showed adequate target coverage (V95%Rx=>95%), better dose conformity and gradient, while meeting the dose constraints of the OARs. Excellent NTHT sparing is achieved by reducing the volumes of V20Gy by 43 cc and V5Gy by 250 cc. Average mean dose reduction of 2.5 (range: 0.6 – 6.0) Gy and 2.2 (0.7 – 5.7 Gy) was observed in 6X FFF and 10X FFF plans, respectively. Revised plans showed the possibility of treating each arc in a single BH. The standardized technique used in this study showed improved NTHT sparing and better dose conformity. This result may be important for the group of patients where cardiac toxicity may play a vital role in long-term survival. BH treatments may reduce the required PTV margins resulting in further NTHT sparing.Abstract 3778; Table 1Vol. (cc)Plan TypeTarget CoverageConformityMean D (Gy)%VRx%V95%RxConformity IndexGradient MeasureITV48.1 ± 29Clinical38.4 ± 1.197.6 ± 2.499.7 ± 0.66X FFF36.9 ± 0.494.2 ± 3.199.3 ± 0.810X FFF36.8 ± 0.890.5 ± 11.698.7 ± 2.0PTV138.9 ± 67.8Clinical33.6 ± 1.199.0 ± 0.899.7 ± 0.41.14 ± 0.122.01 ± 0.476X FFF32.3 ± 0.493.8 ± 2.596.8 ± 2.21.02 ± 0.041.76 ± 0.4710X FFF32.3 ± 0.494.2 ± 2.397.1 ± 1.81.03 ± 0.031.55 ± 0.26Non-Target Heart TissueMean D (Gy)%V25%V20%V15%V10%V5%V2Clinical6.2 ± 2.10.9 ± 0.84.9 ± 2.511.2 ± 5.421.4 ± 9.140.5 ± 13.966.7 ± 17.86X FFF3.7 ± 1.10.3 ± 0.31.9 ± 2.74.9 ± 1.610.1 ± 3.622.5 ± 8.945.9 ± 15.7Vol. spared (cc)9 ± 1143.± 3590 ± 76160 ± 113250 ± 146284 ± 20910X FFF4.0 ± 1.10.4 ± 0.32.2 ± 0.75.5 ± 1.711.4 ± 3.825.5 ± 9.649.6 ± 16.5Vol. spared (cc)8 ± 1039 ± 3381 ± 75142 ± 108208 ± 111233 ± 150 Open table in a new tab

Whole brain irradiation with simultaneous integrated boost in treatment of oligometastatic brain disease

Background/Aim. Brain metastases occur in 20%?30% of all patients with systemic cancer. We aimed at investigating whether patients with oligometastatic brain disease treated with whole brain radiotherapy (WBRT) and simultaneous integrated boost of brain metastases (SIBmets) improved overall survival (clinical outcomes) compared with patients from the Radiation Therapy Oncology Group (RTOG) 9508 database, treated with WBRT and sequential stereotactic radiosurgery (SRS) boost. Methods. WBRT with SIBmets, using the RapidArc (RA) (Varian Medical Systems, Palo Alto, CA) volumetric modulated arc technique (VMAT), was delivered to 15 patients with computed tomography/ magnetic resonance imaging (CT/MRI) findings of 1?3 brain metastases with a diameter less than 40 mm for the largest lesion. Radiotherapy (RT) plans consisted of WBRT, with a prescribed dose of 20 Gy in 5 fractions, with SIBmets which was also 20 Gy (gray units) in 5 fractions. Results. A group of 15 patients included 8 males and 7 females with the mean age of 56.3 years. Three patients were in the RTOG Recursive Partitioning Analysis (RPA) Class I and other 12 patients in RPA Class II. Four patients had one metastasis and 11 patients had two metastases. Calculated mean survival time (MST) was 7.49 ? 4.36 months with no statistically significant difference compared to RTOG 9508 results (MST = 6.5 months) (p = 0.197). The local control rate for 7 patients after three months was 85.7%. Conclusion. WBRT with SIBmets and WBRT + SRS are clinically equivalent treatment options for the patients with oligometastatic brain disease. In comparison to the WBRT + SRS, the treatment by WBRT + SIBmets technique reduces the treatment time and improves the patient?s treatment comfort.

Linac-based stereotactic body radiation therapy for unresectable locally advanced pancreatic cancer: risk-adapted dose prescription and image-guided delivery.

Stereotactic body radiation therapy (SBRT) represents a new treatment option for locally advanced pancreatic cancer (LAPC). An accurate treatment planning with risk-adapted dose prescription with adherence to specific dose constraints for organs at risk (OARs) and the use of daily cone beam CT (CBCT) for image guidance could allow an effective and safe treatment delivery. Here, feasibility and efficacy of SBRT in LAPC treated in our cancer care center are reported. 33 unresectable LAPC patients underwent SBRT. In order to respect OAR dose constraints, a risk-adapted dose prescription strategy was adopted, choosing between the following schedules: 42 Gy or 45 Gy in 6 daily fractions with a biologically effective dose (BED) > 70 Gy10 or 36 Gy/6fractions (estimating aBED 57.6 Gy10). SBRT was delivered with volumetric modulated arc technique (VMAT) and flattening filter-free (FFF) mode. Image guidance was performed by means of CBCT before every treatment session. The patients were evaluated at the end of treatment for acute toxicity and at 3, 6, and 12 months for late toxicity and treatment response. At the time of analysis, the median follow-up was 18months (range 5-34months). Prior to SBRT, 24 out of 33patients received induction chemotherapy. Although all patients were previously judged as unresectable, 6 out of 33 (18%) underwent surgery after SBRT; all of them received aBED > 70 Gy10. One-year LC and OS were 81% and 75%, respectively. A total of 12patients (37%) had an extra-pancreatic progression. No cases of ≥G3 acute or late toxicity were reported. In our experience, risk-adapted dose prescription and image-guided SBRT represents an effective treatment option for LAPC patients.

Limitations of Optimization Algorithm With Volumetric Modulated Arc Technique for Head and Neck Cancer Radiation Therapy

Limitations of Optimization Algorithm With Volumetric Modulated Arc Technique for Head and Neck Cancer Radiation Therapy

Comparison of multi-leaf collimator tracking and treatment-couch tracking during stereotactic body radiation therapy of prostate cancer

Purpose and backgroundMotion mitigation during prostate stereotactic body radiation therapy (SBRT) ensures optimal target coverage while reducing the risk of overdosage of nearby organs. The geometrical and dosimetrical performance of motion mitigation with the multileaf-collimator (MLC tracking) or the treatment couch (couch tracking) were compared. Material and methodsFor ten prostate patients, SBRT treatment plans with integrated boosts were prepared using volumetric modulated arc technique. For the geometrical evaluation, a lead sphere at the beam isocenter was moved according to five prostate motion curves (i) without mitigation, (ii) with MLC tracking or (iii) with couch tracking. During irradiation, MV images were taken and the over-/underexposed areas were evaluated.For the dosimetrical evaluation, the plans were applied to a dosimetric phantom. Dose distributions with and without mitigation were evaluated inside the target structure and organs at risk. ResultsThe median over-/underexposed area was reduced significantly from 2.02cm2 without mitigation to 1.00cm2 and 0.45cm2 with MLC and couch tracking. Closest dosimetrical agreement to the static references was achieved with couch tracking. ConclusionsMLC and couch tracking at a conventional linear accelerator significantly improved the accuracy of prostate SBRT in the presence of motion, whereby couch tracking showed slightly better performance than MLC tracking.