Intraindividual Comparison of Conventional Three-Dimensional Radiotherapy and Intensity Modulated Radiotherapy in the Therapy of Locally Advanced Non-Small Cell Lung Cancer A Planning Study

Background: Local failure is the one of the most frequent cause of tumor related death in locally advanced non-small cell lung cancer (LAD-NSCLC). Dose escalation has the promise of increased loco-regional tumor control but is limited by the tolerances of critical organs. Patients and Methods: To evaluate the potential of IMRT in comparison to conventional three-dimensional conformal planning (3DCRT) dose constraints were defined: Maximum dose (D_max) to spinal cord < 48 Gy, mean lung dose h 24 Gy, D_max esophagus > 70 Gy in not more than 5 cm of the total length. For ten patients two plans were compared: (1) 3DCRT with 5 weekly fractions (SD) of 2 Gy to a total dose (TD) of 50 Gy to the planning target volume of second order (PTV2). If the tolerance of the critical organs was not exceeded, patients get a boost plan with a higher TD to the PTV1. (2) IMRT: concomitant boost with 5 weekly SD of 2 Gy (PTV1) and 1.5 Gy to a partial (p)PTV (pPTV=PTV2 š PTV1) to a TD of 51 Gy to the pPTV and 68 Gy to the PTV1. If possible, patients get a boost plan to the PTV1 with 5 weekly SD of 2 Gy to the highest possibly TD. Results: Using 3DCRT, 3/10 patients could not be treated with TD > 50 Gy, but 9/10 patients get higher TD by IMRT. TD to the PTV1 could be escalated by 16% on average. The use of non-coplanar fields in IMRT lead to a reduction of the irradiated lung volume. There is a strong correlation between physical and biological mean lung doses. Conclusion: IMRT gives the possibility of further dose escalation without an increasing mean lung dose especially in patients with large tumors. Hintergrund: Lokale Rezidive sind eine häufige Todesursache bei Patienten mit lokal fortgeschrittenen nichtkleinzelligen Bronchialkarzinomen (LAD-NSCLC). Dosiseskalation verspricht hier eine Verbesserung der lokalen Kontrolle, ist aber limitiert durch die Toleranz der Nachbarstrukturen. Patienten und Methoden: Um das Potential der IMRT im Vergleich zur konventionellen 3-D-Planung herauszuarbeiten, wurden folgende Dosis-Volumen-Vorgaben definiert: Maximale Dosis (D_max) des Myelons < 48 Gy, mittlere Lungendosis (MLD) h 24 Gy, D_max des Ösophagus > 70 Gy in h 5 cm der Gesamtlänge. Für zehn Patienten mit LAD-NSCLC wurden verglichen: 1. 3DCRT mit fünf wöchentlichen Einzeldosen (ED) von 2 Gy bis zu einer Gesamtdosis (GD) von 50 Gy für das Planungszielvolumen zweiter Ordnung (PTV2). Wenn die Toleranz der umliegenden Gewebe dies zuließ, erhielten die Patienten einen Boostplan für das PTV1. 2. IMRT: Concomitant Boost mit fünf söchentlichen ED von 2 Gy für das PTV1 und 1,5 Gy für das partielle PTV (pPTV=PTV2 š PTV1) bis zu einer GD von 51 Gy im pPTV und 68 Gy im PTV1. Falls die Belastung des Normalgewebes dies erlaubte, erfolgte ein Boostplan für das PTV1 mit fünf wöchentlichen ED von 2 Gy bis zur höchstmöglichen GD. Ergebnisse: Konventionell konnten 3/10 Patienten mit GD > 50 Gy behandelt werden - mittels IMRT konnten bei 9/10 Patienten höhere Dosen appliziert werden. Im PTV1 konnte im Mittel eine Dosiseskalation von 16% erreicht werden. Besonders Patienten mit großen Tumoren profitierten von der IMRT. Die Verwendung nonkoplanarer Techniken führte zur Verringerung der Dosis innerhalb des kritischen Lungenvolumens. Die physikalischen mittleren Lungendosen waren hoch korreliert mit den biologisch gewichteten mittleren Lungendosen. Schlussfolgerung: Im Vergleich zur 3DCRT ermöglicht die IMRT eine Dosiseskalation in der Behandlung von LAD-NSCLC ohne Erhöhung der mittleren Lungendosis. Von der Technik profitieren insbesondere Patienten mit größeren Tumoren.     

Reducing the Risk of Xerostomia and Mandibular Osteoradionecrosis: The Potential Benefits of Intensity Modulated Radiotherapy in Advanced Oral Cavity Carcinoma

Radiation therapy for squamous cell carcinoma of the oral cavity may be curative, but carries a risk of permanent damage to bone, salivary glands, and other soft tissues. We studied the potential of intensity modulated radiotherapy (IMRT) to improve target volume coverage, and normal tissue sparing for advanced oral cavity carcinoma (OCC). Six patients with advanced OCC requiring bilateral irradiation to the oral cavity and neck were studied. Standard 3D conformal radiotherapy (3DCRT) and inverse-planned IMRT dose distributions were compared by using dose-volume histograms. Doses to organs at risk, including spinal cord, parotid glands, and mandible, were assessed as surrogates of radiation toxicity. PTV1 mean dose was 60.8 ± 0.8 Gy for 3DCRT and 59.8 ± 0.1 Gy for IMRT (p = 0.04). PTV1 dose range was 24.7 ± 6 Gy for 3DCRT and 15.3 ± 4 Gy for IMRT (p = 0.001). PTV2 mean dose was 54.5 ± 0.8 Gy for 3DCRT and for IMRT was 54.2 ± 0.2 Gy (p = 0.34). PTV2 dose range was improved by IMRT (7.8 ± 3.2 Gy vs. 30.7 ± 12.8 Gy, p = 0.006). Homogeneity index (HI) values for PTV2 were closer to unity using IMRT (p = 0.0003). Mean parotid doses were 25.6 ± 2.7 Gy for IMRT and 42.0 ± 8.8 Gy with 3DCRT (p = 0.002). The parotid V30 in all IMRT plans was <45%. The mandible V50, V55, and V60 were significantly lower for the IMRT plans. Maximum spinal cord and brain stem doses were similar for the 2 techniques. IMRT provided superior target volume dose homogeneity and sparing of organs at risk. The magnitude of reductions in dose to the salivary glands and mandible are likely to translate into reduced incidence of xerostomia and osteoradionecrosis for patients with OCC.     

Development of a simultaneous boost IMRT class solution for a hypofractionated prostate cancer protocol

The purpose of this work was to develop a robust technique for planning intensity-modulated radiation therapy (IMRT) for prostate cancer patients who are to be entered into a proposed hypofractionated dose escalation study. In this study the dose escalation will be restricted to the prostate alone, which may be regarded as a concurrent boost volume within the overall planning target volume (PTV). The dose to the prostate itself is to be delivered in 3 Gy fractions, and for this phase of the study the total prostate dose will be 57 Gy in 19 fractions, with 50 Gy prescribed to the rest of the PTV. If acute toxicity results are acceptable, the next phase will escalate doses to 60 Gy in 20 x 3 Gy fractions. There will be 30 patients in each arm. This work describes the class solution which was developed to create IMRT plans for this study, and which enabled the same set of inverse planning parameters to be used during optimization for every patient with minimal planner intervention. The resulting dose distributions were compared with those that would be achieved from a 3D conformal radiotherapy (3DCRT) technique that used a multileaf collimator (MLC) but no intensity modulation to treat the PTV, followed by a sequential boost to raise the prostate to 57 Gy. The two methods were tested on anatomical data sets for a series of 10 patients who would have been eligible for this study, and the techniques were compared in terms of doses to the target volumes and the organs at risk. The IMRT method resulted in much greater sparing of the rectum and bladder than the 3DCRT technique, whilst still delivering acceptable doses to the target volumes. In particular, the volume of rectum receiving the minimum PTV dose of 47.5 Gy was reduced from a mean value of 36.9% (range 23.4% to 61.0%) to 18.6% (10.3% to 29.0%). In conclusion, it was found possible to use a class solution approach to produce IMRT dose escalated plans. This IMRT technique has since been implemented clinically for patients enrolled in the hypofractionated dose escalation study.     

A dosimetric evaluation of dose escalation for the radical treatment of locally advanced vulvar cancer by intensity-modulated radiation therapy

The purpose of this planning study was to determine whether intensity-modulated radiation therapy (IMRT) reduces the radiation dose to organs at risk (OAR) when compared with 3D conventional radiation therapy (3D-CRT) in patients with vulvar cancer treated by irradiation. This study also investigated the use of sequential IMRT boost (seq-IMRT) and simultaneous integrated boost (SIB-IMRT) for dose escalation in the treatment of locally advanced vulvar cancer. Five vulvar cancer patients treated in the postoperative setting and 5 patients treated with definitive intent (def-group) were evaluated. For the postoperative group, 3D-CRT and IMRT plans to a total dose (TD) of 45 Gy were generated. For the def-group, 4 plans were generated: a 3D-CRT and an IMRT plan to a TD of 56.4 Gy, a SIB-IMRT plan to a TD of 56 Gy, and a SIB-IMRT with dose escalation (SIB-IMRT-esc): TD of 67.2 Gy. Mean dose and dose-volume histograms were compared using Student's t-test. IMRT significantly (all p < 0.05) reduced the D_mean, V30, and V40 for all OAR in the adjuvant setting. The V45 was also significantly reduced for all OAR except the bladder. For patients treated in the def-group, all IMRT techniques significantly reduced the D_mean, V40, and V45 for all OAR. The mean femur doses with SIB-IMRT and SIB-IMRT-esc were 47% and 49% lower compared with 3D-CRT. SIB-IMRT-esc reduced the doses to the OAR compared with seq-3D-CRT but increased the D_max. for the small bowel, rectum, and bladder. IMRT reduces the dose to the OAR compared with 3D-CRT in patients with vulvar cancer receiving irradiation to a volume covering the vulvar region and nodal areas without compromising the dosimetric coverage of the target volume. IMRT for vulvar cancer is feasible and an attractive option for dose escalation studies.     

Comparison of intensity-modulated radiotherapy with three-dimensional conformal radiation therapy planning for glioblastoma multiforme

This study was designed to assess the feasibility and potential benefit of using intensity-modulated radiotherapy (IMRT) planning for patients newly diagnosed with glioblastoma multiforme (GBM). Five consecutive patients with confirmed histopathologically GBM were entered into the study. These patients were planned and treated with 3-dimensional conformal radiation therapy (3DCRT) using our standard plan of 3 noncoplanar wedged fields. They were then replanned with the IMRT method that included a simultaneous boost to the gross tumor volume (GTV). The dose distributions and dose-volume histograms (DHVs) for the planning treatment volume (PTV), GTV, and the relevant critical structures, as obtained with 3DCRT and IMRT, respectively, were compared. In both the 3DCRT and IMRT plans, 59.4 Gy was delivered to the GTV plus a margin of 2.5 cm, with doses to critical structures below the tolerance threshold. However, with the simultaneous boost in IMRT, a higher tumor dose of 70 Gy could be delivered to the GTV, while still maintaining the uninvolved brain at dose levels of the 3DCRT technique. In addition, our experience indicated that IMRT planning is less labor intensive and time consuming than 3DCRT planning. Our study shows that IMRT planning is feasible and efficient for radiotherapy of GBM. In particular, IMRT can deliver a simultaneous boost to the GTV while better sparing the normal brain and other critical structures.     

Inverse planning in three-dimensional conformal and intensity-modulated radiotherapy of mid-thoracic oesophageal cancer

The aim of this study is to demonstrate the use of inverse planning in three-dimensional conformal radiation therapy (3DCRT) of oesophageal cancer patients and to evaluate its dosimetric results by comparing them with forward planning of 3DCRT and inverse planning of intensity-modulated radiotherapy (IMRT). For each of the 15 oesophageal cancer patients in this study, the forward 3DCRT, inverse 3DCRT and inverse IMRT plans were produced using the FOCUS treatment planning system. The dosimetric results and the planner's time associated with each of the treatment plans were recorded for comparison. The inverse 3DCRT plans showed similar dosimetric results to the forward plans in the planning target volume (PTV) and organs at risk (OARs). However, they were inferior to that of the IMRT plans in terms of tumour control probability and target dose conformity. Furthermore, the inverse 3DCRT plans were less effective in reducing the percentage lung volume receiving a dose below 25 Gy when compared with the IMRT plans. The inverse 3DCRT plans delivered a similar heart dose as in the forward plans, but higher dose than the IMRT plans. The inverse 3DCRT plans significantly reduced the operator's time by 2.5 fold relative to the forward plans. In conclusion, inverse planning for 3DCRT is a reasonable alternative to the forward planning for oesophageal cancer patients with reduction of the operator's time. However, IMRT has the better potential to allow further dose escalation and improvement of tumour control.     

Helical tomotherapy for radiotherapy in esophageal cancer: a preferred plan with better conformal target coverage and more homogeneous dose distribution.

We compare different radiotherapy techniques-helical tomotherapy (tomotherapy), step-and-shoot IMRT (IMRT), and 3-dimensional conformal radiotherapy (3DCRT)-for patients with mid-distal esophageal carcinoma on the basis of dosimetric analysis. Six patients with locally advanced mid-distal esophageal carcinoma were treated with neoadjuvant chemoradiation followed by surgery. Radiotherapy included 50 Gy to gross planning target volume (PTV) and 45 Gy to elective PTV in 25 fractions. Tomotherapy, IMRT, and 3DCRT plans were generated. Dose-volume histograms (DVHs), homogeneity index (HI), volumes of lung receiving more than 10, 15, or 20 Gy (V(10), V(15), V(20)), and volumes of heart receiving more than 30 or 45 Gy (V(30), V(45)) were determined. Statistical analysis was performed by paired t-tests. By isodose distributions and DVHs, tomotherapy plans showed sharper dose gradients, more conformal coverage, and better HI for both gross and elective PTVs compared with IMRT or 3DCRT plans. Mean V(20) of lung was significantly reduced in tomotherapy plans. However, tomotherapy and IMRT plans resulted in larger V(10) of lung compared to 3DCRT plans. The heart was significantly spared in tomotherapy and IMRT plans compared to 3DCRT plans in terms of V(30) and V(45). We conclude that tomotherapy plans are superior in terms of target conformity, dose homogeneity, and V(20) of lung.     

Local High-Dose Radiotherapy and Sparing of Normal Tissue Using Intensity-Modulated Radiotherapy (IMRT) for Mucosal Melanoma of the Nasal Cavity and Paranasal Sinuses

PURPOSE: To evaluate the clinical outcome of intensity-modulated radiotherapy (IMRT) in patients with mucosal melanoma (MM) of the nasal cavity and paranasal sinuses. PATIENTS AND METHODS: Between January 1999 and September 2004, eight patients with histologically proven MM of the nasal cavity and paranasal sinuses were treated with IMRT. A median dose of 66 Gy was applied to the macroscopic tumor (gross tumor volume [GTV]; range, 60-68 Gy) as an integrated boost and a median dose of 59 Gy (range, 54-64 Gy) to the clinical target volume (CTV) with IMRT. RESULTS: Treatment-related toxicity was very mild in most patients. Overall survival was 80% at 5 years. Calculated from treatment with IMRT as primary radiotherapy, survival was 100% at 1 year and 75% at 3 years. After IMRT, local progression-free survival was 71.4% at 1 year and 57.1% at 3 years, respectively. Distant progression-free survival after IMRT was 57.1% at 1 year and 28.6% at 3 years. CONCLUSION: Local dose escalation with IMRT yields good treatment results with respect to local and distant tumor control as well as survival, while treatment-related toxicity can be minimized.     

Adaptive Radiation Therapy for Localized Mesothelioma with Mediastinal Metastasis Using Helical Tomotherapy

The purpose of this study was to compare 2 adaptive radiotherapy strategies with helical tomotherapy. A patient having mesothelioma with mediastinal nodes was treated using helical tomotherapy with pretreatment megavoltage CT (MVCT) imaging. Gross tumor volumes (GTVs) were outlined on every MVCT study. Two alternatives for adapting the treatment were investigated: (1) keeping the prescribed dose to the targets while reducing the dose to the OARs and (2) escalating the target dose while maintaining the original level of healthy tissue sparing. Intensity modulated radiotherapy (step-and-shoot IMRT) and 3D conformal radiotherapy (3DCRT) plans for the patient were generated and compared. The primary lesion and nodal mass regressed by 16.2% and 32.5%, respectively. Adapted GTVs and reduced planning target volume (PTV) margins of 4 mm after 22 fractions decrease the planned mean lung dose by 19.4%. For dose escalation, the planned prescribed doses may be increased from 50.0 to 58.7 Gy in PTV₁ and from 60.0 to 70.5 Gy in PTV₂. The step-and-shoot IMRT plan was better in sparing healthy tissue but did not provide target coverage as well as the helical tomotherapy plan. The 3DCRT plan resulted in a prohibitively high planned dose to the spinal cord. MVCT studies provide information both for setup correction and plan adaptation. Improved healthy tissue sparing and/or dose escalation can be achieved by adaptive planning.     

Simultaneous Integrated Boost (SIB) for Nasopharynx Cancer with Helical Tomotherapy

PURPOSE: To explore the potential of helical tomotherapy (HT) in the treatment of nasopharynx cancer. PATIENTS AND METHODS: Six T1-4 N1-3 patients were considered. A simultaneous integrated boost (SIB) technique was planned with inversely optimized conventional intensity-modulated radiotherapy (IMRT; dynamic multileaf collimator using the Eclipse-Helios Varian system) and HT. The prescribed (median) doses were 54 Gy, 61.5 Gy, and 64.5 Gy delivered in 30 fractions to PTV1 (planning target volume), PTV2, and PTV3, respectively. The same constraints for PTV coverage and for parotids, spinal cord, mandible, optic structures, and brain stem were followed in both modalities. The planner also tried to reduce the dose to other structures (mucosae outside PTV1, larynx, esophagus, inner ear, thyroid, brain, lungs, submental connective tissue, bony structures) as much as possible. RESULTS: The fraction of PTV receiving >95% of the prescribed dose (V95%) increased from 97.6% and 94.3% (IMRT) to 99.6% and 97% (HT) for PTV1 and PTV3, respectively (p<0.05); median dose to parotids decreased from 30.1 Gy for IMRT to 25.0 Gy for HT (p<0.05). Significant gains (p<0.05) were found for most organs at risk (OARs): mucosae (V30 decreased from 44 cm(3) [IMRT] to 18 cm(3) [HT]); larynx (V30: 25 cm(3) vs. 11 cm(3)); thyroid (mean dose: 48.7 Gy vs. 41.5 Gy); esophagus (V45: 4 cm(3) vs. 1 cm(3)); brain stem (D1%: 45.1 Gy vs. 37.7 Gy). CONCLUSION: HT improves the homogeneity of dose distribution within PTV and PTV coverage together with a significantly greater sparing of OARs compared to linac five-field IMRT.     

IMRT to Escalate the Dose to the Prostate while Treating the Pelvic Nodes

Background and Purpose: To assess and quantify the benefit of introducing intensity–modulated radiotherapy (IMRT) over conventional approaches to cover the pelvic nodes while escalating the dose to the prostate gland.Material and Methods: The pelvic lymphatics were planned to receive 50 Gy at 2 Gy per fraction by four–field box (4FB) technique and standard field blocks drawn on digitally reconstructed radiographs (DRR), 4FB with field blocks according to the position of pelvic nodes as contoured on serial planning CT slices, or IMRT. The lateral fields included three different variations of field blocks to assess the role of various degrees of rectal shielding. The boost consisted in 26 Gy in 13 fractions delivered via six–field three–dimensional conformal radiotherapy (3DCRT) or IMRT. By the combination of a pelvic treatment and boost, several plans were obtained for each patient, all normalized to be isoeffective with regard to prostate–planning target volume (PTV–P) coverage. Plans were compared with respect to dose–volume histogram (DVH) of pelvic nodes/seminal vesicles–PTV (PTV–PN/SV), rectum, bladder and intestinal cavity. Reported are the results obtained in eight patients.Results: Pelvic IMRT with a conformal boost provided superior sparing of both bladder and rectum over any of the 4FB plans with the same boost. For the rectum the advantage was around 10% at V70 and even larger for lower doses. Coverage of the pelvic nodes was adequate with initial IMRT with about 98% of the volume receiving 100% of the prescribed dose. An IMRT boost provided a gain in rectal sparing as compared to a conformal boost. However, the benefit was always greater with pelvic IMRT followed by a conformal boost as compared to 4FB with IMRT boost. Finally, the effect of utilizing an IMRT boost with initial pelvic IMRT was greater for the bladder than for the rectum (at V70, about 9% and 3% for the bladder and rectum, respectively).Conclusion: IMRT to pelvic nodes with a conformal boost allows dose escalation to the prostate while respecting current dose objectives in the majority of patients and it is dosimetrically superior to 4FB. An IMRT boost should be considered for patients who fail to meet bladder dose objectives.     

Dose Escalation in Large Anterior Skull-Base Tumors by Means of IMRT

PURPOSE: To evaluate the feasibility and tolerance of dose escalation with stereotactic intensity-modulated radiotherapy (sIMRT) for skull-base tumors. PATIENTS AND METHODS: Between 01/2003 and 12/2004, twelve patients were treated. Nine were exclusively treated at the Novalis site with one planning target volume (PTV) field boost, three were administered boost IMRT treatment (two with each one PTV-shrinking field, one with single PTV) after conventional three-dimensional conformal radiotherapy. This resulted in 23 PTVs with a median volume of 93.63 cm3 (range, 88.58-125.88 cm3). Dose calculation was done by the pencil-beam algorithm. Median total doses of 66.6, 77.4, and 63.9 Gy were prescribed for sIMRT alone, sIMRT after 3-D conformal irradiation of the nasopharynx and cervical lymph nodes with 59.4 Gy, and for reirradiation, respectively. RESULTS: 95% isodose PTV coverage was reached in 86.5% (range, 80-93%). Homogeneity (Dmax/Dref) was 1.11, 1.09, and 1.08. Median total doses to 50% of chiasm, right and left optic nerve were 16.21, 16.82 and 10.23 Gy. 11/12 patients are locally controlled with a median follow-up of 11 months (range, 3-23 months), one has died of pulmonary embolism after cerebrospinal dissemination of retinal adenocarcinoma. CONCLUSION: SIMRT enables dose escalation to tumors located close to critical organs. Inverse planning for micro-multileaf collimator stereotactic irradiation is practicable in the daily routine irradiation program. SIMRT needs special verification and still, the following parameters have to be standardized: IMRT dose specification, dose maxima, length of radiation delivery time.     

Intensity modulated radiation therapy versus three dimensional conformal radiation therapy for treatment of high grade glioma: a radiobiological modeling study

Treatment of glioblastoma results in a median survival of 12 months. Radiation dose escalation trials for high grade gliomas have resulted in modest improvements in survival in selected patients with small peripheral tumors at the expense of normal brain toxicity. Neurotoxicity includes radiation necrosis but it is increasingly recognized that long-term survivors may develop neuro-cognitive deficits. Tumor control probability (TCP) and normal tissue complication probability (NTCP) are radiobiological models used to predict treatment outcomes. This study assesses the impact of radiation dose escalation from 59.6 Gy to 90 Gy on TCP and NTCP in ten patients planned with Three Dimensional Conformal Therapy (3DCRT) and Intensity Modulated Radiation Therapy (IMRT). No difference in TCP was observed between 3DCRT and IMRT at doses of 59.4 Gy and 90 Gy. However, dose escalation to 90 Gy resulted in about 25% relative TCP increase. Compared to 3DCRT, dose escalation with IMRT significantly reduced NTCP by 70% (10.75% v. 3.75%, respectively). As a result, highly conformal techniques are recommended to obviate radiation exposure of normal brain especially when radiation dose escalation is used. Further understanding of the molecular mechanisms underlying neurotoxicity will allow the development of more precise radiobiological predictive models and of approaches to prevent or treat radiation-induced brain damage.     

Adjuvant Radiotherapy for Gastric Cancer: A Dosimetric Comparison of 3-Dimensional Conformal Radiotherapy,Tomotherapy® and Conventional Intensity Modulated Radiotherapy Treatment Plans

Some patients with gastric cancer benefit from post-operative chemo-radiotherapy, but adequately irradiating the planning target volume (PTV) whilst avoiding organs at risk (OAR) can be difficult. We evaluate 3-dimensional conformal radiotherapy (CRT), conventional intensity-modulated radiotherapy (IMRT) and helical tomotherapy (TT). TT, 2 and 5-field (F) CRT and IMRT treatment plans with the same PTV coverage were generated for 5 patients and compared. Median values are reported. The volume of left/right kidney receiving at least 20Gy (V20) was 57/51% and 51/60% for 2 and 5F-CRT, and 28/14% for TT and 27/19% for IMRT. The volume of liver receiving at least 30Gy (V30) was 45% and 62% for 2 and 5F-CRT, and 37% for TT and 35% for IMRT. With TT, 98% of the PTV received 95-105% of the prescribed dose, compared with 45%, 34% and 28% for 2F-CRT, 5F-CRT and IMRT respectively. Using conventional metrics, conventional IMRT can achieve comparable PTV coverage and OAR sparing to TT, but at the expense of PTV dose heterogeneity. Both irradiate large volumes of normal tissue to low doses. Additional studies are needed to demonstrate the clinical impact of these technologies.     

Superiority of conventional intensity-modulated radiotherapy over helical tomotherapy in locally advanced non-small cell lung cancer

PURPOSE: To compare helical tomotherapy (HT) and conventional intensity-modulated radiotherapy (IMRT) using a variety of dosimetric and radiobiologic indexes in patients with locally advanced non-small cell lung cancer (LA-NSCLC). PATIENTS AND METHODS: A total of 20?patients with LA-NSCLC were enrolled. IMRT plans with 4-6 coplanar beams and HT plans were generated for each patient. Dose distributions and dosimetric indexes for the tumors and critical structures were computed for both plans and compared. RESULTS: Both modalities created highly conformal plans. They did not differ in the volumes of lung exposed to >?20?Gy of radiation. The average mean lung dose, volume receiving ≥?30?Gy, and volume receiving ≥?10?Gy in HT planning were 18.3?Gy, 18.5%, and 57.1%, respectively, compared to 19.4?Gy, 25.4%, and 48.9%, respectively, with IMRT (p?=?0.004, p?相似文献   

Volumetric-modulated arc radiotherapy for pancreatic malignancies: Dosimetric comparison with sliding-window intensity-modulated radiotherapy and 3-dimensional conformal radiotherapy

Volumetric-modulated arc radiotherapy (VMAT) is an iteration of intensity-modulated radiotherapy (IMRT), both of which deliver highly conformal dose distributions. Studies have shown the superiority of VMAT and IMRT in comparison with 3-dimensional conformal radiotherapy (3D-CRT) in planning target volume (PTV) coverage and organs-at-risk (OARs) sparing. This is the first study examining the benefits of VMAT in pancreatic cancer for doses more than 55.8 Gy. A planning study comparing 3D-CRT, IMRT, and VMAT was performed in 20 patients with pancreatic cancer. Treatments were planned for a 25-fraction delivery of 45 Gy to a large field followed by a reduced-volume 8-fraction external beam boost to 59.4 Gy in total. OARs and PTV doses, conformality index (CI) deviations from 1.0, monitor units (MUs) delivered, and isodose volumes were compared. IMRT and VMAT CI deviations from 1.0 for the large-field and the boost plans were equivalent (large field: 0.032 and 0.046, respectively; boost: 0.042 and 0.037, respectively; p > 0.05 for all comparisons). Both IMRT and VMAT CI deviations from 1.0 were statistically superior to 3D-CRT (large field: 0.217, boost: 0.177; p < 0.05 for all comparisons). VMAT showed reduction of the mean dose to the boost PTV (VMAT: 61.4 Gy, IMRT: 62.4 Gy, and 3D-CRT: 62.3 Gy; p < 0.05). The mean number of MUs per fraction was significantly lower for VMAT for both the large-field and the boost plans. VMAT delivery time was less than 3 minutes compared with 8 minutes for IMRT. Although no statistically significant dose reduction to the OARs was identified when comparing VMAT with IMRT, VMAT showed a reduction in the volumes of the 100% isodose line for the large-field plans. Dose escalation to 59.4 Gy in pancreatic cancer is dosimetrically feasible with shorter treatment times, fewer MUs delivered, and comparable CIs for VMAT when compared with IMRT.     

Exploring the Feasibility of Dose Escalation Positron Emission Tomography–Positive Disease with Intensity-Modulated Radiation Therapy and the Effects on Normal Tissue Structures for Thoracic Malignancies

The pattern of failure is one of the major causes of mortality among thoracic patients. Studies have shown a correlation between local control and dose. Intensity-modulated radiation therapy (IMRT) has resulted in conformal dose distributions while limiting dose to normal tissue. However, thoracic malignancies treated with IMRT to highly conformal doses up to 70 Gy still have been found to fail. Thus, the need for dose escalation through simultaneous integrated boost (SIB) may prove effective in minimizing reoccurrences. For our study, 28 thoracic IMRT plans were reoptimized via dose escalation to the gross tumor volume (GTV) and planning target volume (PTV) of 79.2 Gy and 68.4 Gy, respectively. Reoccurrences in surrounding regions of microscopic disease are rare therefore, dose-escalating regional nodes (outside GTV) were not included. Hence, the need to edit GTV margins was acceptable for our retrospective study. A median dose escalation of approximately 15 Gy (64.8–79.2 Gy) via IMRT using SIB was deemed achievable with minimal percent differences received by critical structures compared with the original treatment plan. The target's mean doses were significantly increased based on p-value analysis, while the normal tissue structures were not significantly changed.     

Hypofractionated Stereotactic Radiotherapy for Primary and Secondary Intrapulmonary Tumors

PURPOSE: To evaluate the feasibility, efficacy, and side effects of dose escalation in hypofractionated stereotactic radiotherapy (hfSRT) for intrapulmonary tumors with the Novalis system (BrainLAB AG, Heimstetten, Germany). PATIENTS AND METHODS: From 07/2003 to 01/2005, 21 patients/39 tumors were treated with 5 x 7 Gy (n = 21; total dose 35 Gy) or 5 x 8 Gy (n = 18; total dose 40 Gy). There were three cases of primary lung cancer, the remainder were metastases. Median gross tumor volume (GTV) and planning target volume (PTV) were 2.89 cm(3) (range, 0.15-67.94 cm(3)) and 25.75 cm(3) (range, 7.18-124.04 cm(3)), respectively. RESULTS: Rates of complete remission, partial remission, no change, and progressive disease were 51%, 33%, 3%, and 13%, respectively. No grade 4 toxicity occurred, nearly all patients had grade 1 initially. One grade 3 toxicity, i.e., dyspnea, was documented for a period of 6 months after therapy. Radiosurgery quality assurance guidelines could be met. CONCLUSION: hfSRT of primary and secondary lung tumors using a schedule of five fractions at 7-8 Gy each was well tolerated. Further dose escalation is planned.     

Conformal breast irradiation with the arm of the affected side parallel to the body

Purpose

To propose a simple, forward-planned three-dimensional conformal radiotherapy (3D-CRT) technique for breast cancer patients with frozen shoulder.

Materials and methods

A technique is described that avoids lateral beams transmitting through the arm of the affected side. One medial, tangentially applied beam deposits most of the dose. Further beams with little weight are used to attain dose homogeneity. In order to quantify dose distribution and homogeneity in the planning target volume (PTV), as well as the scattered dose in organs at risk (OAR), the parameters D95, D5, D1, mean and median dose were determined for the individual volumes. Intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) plans were created in order to compare these with the proposed technique.

Results

The described technique achieved homogenous dose deposition within the PTV. A regimen comprising 25 fractions of 2 Gy prescribed to the PTV resulted in the following dose parameters: PTV(D95): 44.3 Gy, PTV(D5): 52.7 Gy, PTV(D1): 54.8 Gy, PTV(mean): 49.3 Gy and PTV(median): 49.9 Gy. Mean lung dose was 7.0 Gy. The ipsilateral lung received a mean dose of 9.9 Gy. This plan was accepted for treatment. The IMRT and VMAT plans achieved a similar dose distribution in the PTV. These techniques also reduced dose deposition in the OAR.

Conclusion

The proposed 3D-CRT technique allows treatment of breast cancer patients who are not able to raise their arms above their head. Homogenous dose distribution in the PTV was achieved while avoiding lateral beams that transmit through the arm of the affected side. Mean lung dose was comparable to that of the conventional technique using opposed tangential beams. IMRT and VMAT also provide good target dose homogeneity with good sparing of OAR. However, these techniques are more demanding in terms of planning and quality assurance.