Data from the randomized Intergroup Trial 116 suggest effectiveness of adjuvant radiochemotherapy in patients with advanced gastric cancer. Late toxicity, however, especially with respect to the ...kidneys, may pose significant longtime problems. Intensity-modulated radiotherapy (IMRT) may reduce toxicity to organs at risk. To evaluate the relative merits of different IMRT approaches, we performed a plan comparison between a step-and-shoot class solution and an AP-PA setup, a conventional box technique and the Peacock tomotherapy approach.
Computed tomographies and structure data from 15 patients who had been treated postoperatively for advanced (T3/T4/N+) gastric cancer at our department formed the basis of our plan comparison study. For each patient data set, 5 plans or plan combinations (conventional 3D plan, AP-PA plan, step-and-shoot IMRT, tomotherapy with 1-cm or 2-cm collimation) were chosen, and evaluation was performed for a total dose of 45 Gy delivered as the median dose to the target volume for each plan or plan combination.
Median kidney dose generated from the IMRT plans is reduced individually by >50% for the kidney with the highest exposure (usually the left kidney) from 20 to 30 Gy with conventional 3D planning down to values between 8 and 10 Gy for IMRT. On average, median dose to the right kidney is the same for the conventional box technique and IMRT (between 8 and 10 Gy) but lower for the AP-PA technique. In 3 patients, kidney dose might have been ablative for both kidneys with both the AP-PA technique and the box technique, whereas it was acceptable with IMRT. Median dose to the liver was subcritical with all modalities but lowest with AP-PA fields. Differences between step-and-shoot IMRT and tomotherapy plans are small when compared to the differences between IMRT plans and conventional conformal 3D plans. For some patients, however, their body and target diameters obviate treatment with tomotherapy. Treatment time for the step-and-shoot approach and for tomotherapy with 2-cm collimation can be kept <20 min.
For postoperative radiotherapy of advanced gastric cancer, step-and-shoot IMRT as well as tomotherapy can deliver efficient doses to target volumes while delivering dose to the kidneys in a fashion that is different from a conventional technique and is clearly advantageous in a small number of patients. An advantage for the majority of patients is likely with the normal tissue complication probability data presented in this series, but, given the uncertainty of the reaction of the kidney to inhomogeneous dose distributions, cannot be considered unequivocal at the moment. Different technical limitations apply to the different IMRT techniques. The choice of approach is therefore determined by departmental circumstances.
A new method is described that allows precise modelling of organs at risk and target volume for radiation therapy of intra-ocular tumours. The aim is to optimize the dose distribution and thus to ...reduce normal tissue complication probability. A geometrical 3D model based on elliptic shapes was developed that can be used for multimodal model-based segmentation of 3D patient data. The tumour volume cannot be clearly identified in CT and MR data, whereas the tumour outline can be discriminated very precisely in fundus photographs. Therefore, a multimodal 2D fundus diagram was developed, which allows us to correlate and display simultaneously information extracted from the eye model, 3D data and the fundus photograph. Thus, the connection of fundus diagram and 3D data is well-defined and the 3D volume can be calculated directly from the tumour outline drawn onto the fundus photograph and the tumour height measured by ultrasound. The method allows the calculation of a precise 3D eye model of the patient, including the different structures of the eye as well as the tumour volume. The method was developed as part of the new 3D treatment planning system OCTOPUS for proton therapy of ocular tumours within a national research project together with the Hahn-Meitner-Institut Berlin.
For accurate positioning of the prostate in external radiotherapy, transabdominal ultrasound localization and positioning systems are available. Reports have stated that probe pressure applied during ...image acquisition causes clinically relevant prostate displacement. The aim of this study was to investigate the prostate displacement due to the pressure applied during transabdominal ultrasound image acquisition with the BAT ultrasound system.
For ten patients who had undergone iodine-125 seed implantation for brachytherapy of prostate cancer, X-ray simulations were performed before and during ultrasound image acquisition. The iodine seeds are visible on the X-ray images, representing the position of the prostate. The simulator's crosshair, indicating the isocenter, was used as reference coordinate system. For each patient the change in prostate position was calculated based on the seed positions during and after ultrasound examination.
A maximum displacement of the prostate of 2.3 mm in anteroposterior and 1.9 mm in craniocaudal direction and a rotational change of up to 2.5 degrees were observed. If the system was not handled correctly and too much pressure was applied, a shift of the prostate of up to 10 mm could be induced.
Compared to the prostate displacement due to changes in rectal filling, which according to Crook et al. can be as much as 1.7 cm, the maximum displacement of less than 0.3 cm caused by the probe pressure is negligible. However, proper education of the staff and preparation of the patient are essential for the safe use of the system.
Radiosurgery of liver metastases is effective but a technical challenge due to respiration-induced movement. The authors report on the initial experience of the combination of active breathing ...control (ABC) with stereotactic ultrasound (B-mode acquisition and targeting BAT) for frameless radiosurgery.
A patient with a solitary, inoperable liver metastasis from cholangiocellular carcinoma is presented (Figure 4). ABC (Figure 3) was used for tumor/liver immobilization. Tumor/liver position was controlled and corrected using ultrasound (BAT; Figure 1). The tumor was irradiated with a single dose of 24 Gy.
Using ABC, the motion of the tumor was significantly reduced and the overall positioning error was < 5 mm (Figure 2). BAT allowed a rapid localization of the lesion during breath hold which could be performed without difficulties for 20 s. Overall treatment time was acceptable (30 min).
Frameless stereotactic radiotherapy with the combination of ABC and BAT allows the delivery of high single doses to targets accessible to ultrasound with high precision comparable to a frame-based approach.
Mit der intensitätsmodulierten Strahlentherapie (IMRT) zusammen mit modernen, nichtinvasiven Lokalisationsverfahren steht eine Methodik zur Verfügung, mit der die konformale Bestrahlung des ...Prostatakarzinoms unter optimaler Schonung des Rektums potentiell verbessert werden kann. Diese Übersicht fasst einerseits die klinischen Erfordernisse an die Strahlentherapie beim fortgeschrittenen Prostatakarzinom und andererseits die neuen nichtinvasiven technischen Möglichkeiten zusammen, die helfen, diese Erfordernisse besser zu erfüllen. Zusammen mit der Diskussion der neuen biologischen Daten, die evtl. die Verkürzung der Radiotherapie ermöglichen, wurde versucht, diese Entwicklungen mit ihren theoretischen Vorteilen und eventuellen Problemen zu schildern, um diese Vorgänge über die Strahlentherapie hinaus transparent zu machen. Intensity modulated radiotherapy (IMRT) combined with recently developed noninvasive image-guided targeting techniques for tumor localization/repositioning provide a means to further improve on conformal radiotherapy of prostate cancer by optimally sparing the rectum. This refined approach may potentially improve treatment results for locally advanced prostate cancer while reducing side effects. This review summarizes the clinical requirements for effective prostate radiotherapy and describes the new technology that helps to better fulfil these requirements. These noninvasive developments, their potential benefit as well as their limitations, together with new data on fractionation sensitivity of prostate cancer that may lead to shortened overall treatment times may be of interest for all physicians treating patients with prostate cancer.PUBLICATION ABSTRACT
