Frontiers of Radiation Therapy and Oncology最新文献

Managing target motion first requires understanding the nature of the motion characteristic of the tumor in the individual patient. It is important to have effective immobilization and patient training strategies to help reduce motion, and then to design appropriate margins and compensation for the residual motion that is quantified. Especially when considering complex, technically demanding treatments that require a degree of patient cooperation, careful patient selection is needed to ensure that the potential benefits of the treatment design are actually realized. Finally, accurate treatment hinges critically on verification - of overall positioning, of target and organ motion at the time of treatment, and of the performance of the selected treatment strategy. Properly selected imaging methods are central to this verification process. This discussion will present practical solutions for motion management and image guidance of radiotherapy for thoracic tumors, and most of these concepts are widely applicable to treatment of other tumor sites as well.

Radiation therapy is a key component of the multidisciplinary treatment of head and neck cancers (HNC), which are ideal tumors for intensity-modulated radiation therapy (IMRT) because of their location and intimate relationship to the surrounding critical structures. Several institutional studies have suggested that IMRT is superior to conventional radiation therapy in salivary preservation and holds promises for improved locoregional control of these tumors. Small randomized studies have supported the role of IMRT in reducing xerostomia and possibly improving quality of life. Target delineation for IMRT in these tumors is complex and requires detailed knowledge of head and neck anatomy and pathways of tumor spread. The advent of image-guided radiation therapy offers a new innovation that can refine IMRT delivery even further. This article focuses on the issues surrounding IMRT target delineation for typical HNC presentations and a discussion on the role of FDG-PET imaging in HNC treatment planning.

Radiotherapy planning now uses advanced technologies to accurately image and assess the extent of disease for treatment. PET scanning has become established as perhaps the most important imaging study for patients with Hodgkin's disease. With respect to initial staging, FDG-PET is more sensitive overall than CT scanning. PET can detect disease at sites that do not meet size criteria by CT. Also, PET is more specific than CT alone because of the functional information that it provides. However, some disease may still escape PET imaging, and false negative results can occur. With respect to treatment response, PET has now become accepted as the most important response measure for the lymphomas. Current protocols are investigating the benefit of this information for radiotherapy planning, and even the possible elimination of radiotherapy in patients completely responding to chemotherapy. For radiotherapy planning, PET/CT should be obtained prior to and after chemotherapy; both scans give important information for the design of the radiation treatment. This chapter will review specific guidelines for planning radiotherapy based on these new imaging capabilities.

The radiotherapy treatment process is undergoing rapid development at every step from planning through delivery, and each step is increasingly automated and assisted by new imaging, positioning, contouring and treatment tools. Plan delivery and verification is now aided using an increasing range of image guidance technologies, and imaging at treatment now brings broad opportunities for dose guidance and adaptation for improving overall treatment quality. While these many tools bring exciting opportunities for exact, reliable and efficient targeting of radiation dose, a consistently high level of accuracy must be achieved at every step to achieve the desired results. This level of workmanship requires thorough understanding of the basic methods involved in each step, including the opportunities and limitations, by both the clinicians and the planning/delivery staff alike. These processes and their clinical implementation are discussed in depth throughout this volume. Here, we overview their integration and guiding background concepts, as well as a range of workday efficiencies for clinical practice.

Patients with extensive disease small cell lung cancer (ED-SCLC) represent approximately one-third of all SCLC patients. For these patients, chemotherapy (CHT) is the standard treatment of choice. With CHT given alone, however, there is not a high risk of distant progression, but also progression within the thorax and brain frequently occurs, even in patients achieving a response to CHT. To improve poor figures obtained with CHT alone and address important issue of intrathoracic tumor control and it relationship to overall survival, thoracic radiation therapy (TRT) was introduced with a curative intent in a prospective randomized trial by Jeremic et al (1988-1993). In that trial CHT alone was compared with CHT followed by TRT, and in both groups by a prophylactic cranial irradiation. This trial showed that TRT can offer an improvement on local control that leads to an improvement in overall survival. Toxicity was acceptable, while multivariate analysis identified number of metastasis as an independent prognosticator of outcome. Based on the data of this trial, researchers in the USA and Europe will undergo two prospective trials addressing the issue of TRT in ED-SCLC.

Carcinoma of the lung is the most common cause of cancer-related death in men and women. Prognosis correlates strongly with stage of disease at presentation and to some degree with the histological subtype of the tumor. Histological classifications of lung cancer were some what arbitrary and a matter of convenience. However, multiple lines of differentiation are often found within a single tumor, if it is sufficiently sampled. The new therapeutic approaches especially of non-small cell lung cancer place high demands on pathologists: a clear histological diagnosis with information on the predominant histological subtype is required, obtained by using additional immunohistochemical methods. Using molecular methods, predictive and prognostic factors for adjuvant and neoadjuvant therapies can be identified in tumor cells of small cell lung cancer and non-small cell lung cancer. Biological and molecular factors known in this regard include the epidermal growth factor family and its receptors, K-RAS mutations, neuroendocrine tumor differentiation, and nucleotide-excision-repair proteins (ERCC1 and RRM1). Thymidilate synthase is an interesting target for anticancer agents such as the antifolate pemetrexed. Given the aspect of individualized lung cancer therapy, the collective term small cell/non-small cell lung cancer introduced by the groups of Chuang in1984 and Thomas in 1993 can be regarded as no longer sufficient.

The intrathoracic growth of the tumor causes several severe symptoms as cough, dyspnea, chest pain, hemoptysis, hoarseness, anorexia/nausea, and dysphagia. In patients with manifest or threatening symptoms radiotherapy (RT) as an effective measure should be implemented into the management concept. Palliative RT radiotherapy prefers short hypofractionated schemas (e.g. 10 x 3 Gy, 4 x 5 Gy, 2 x 8 Gy, 1 x 10 Gy). Careful radiation planning supports the precision of palliative RT and reduces significantly the complication rate. A good response and prolonged palliation effects (6-12 months) can be achieved in many cases. However, the minimum biologically equivalent dose should not be less than 35 Gy. RT produces a good outcome in all types of metastases of lung carcinoma. In emergencies like VCSS or spinal cord compression RT should be initiated immediately. The selection of the optimal therapy for locally advanced lung carcinoma with malignant airway obstruction is difficult. Both brachytherapy and percutaneous irradiation are effective, however published results including local a sum of response, functionality and life quality demonstrates more benefit by percutaneous RT. Due to different physical properties of these two methods the combination of brachytherapy and external beam irradiation may be advantageous.

Accurate staging of lung cancer is requisite to choose the optimal therapeutic strategy and is very important for prognosis. Multimodality diagnostic imaging is currently used for detection, staging, and follow-up. Whole-body FDG PET/CT provides 'anatometabolic' information and improves diagnostic accuracy especially for M-staging. MRI has unrivalled tissue contrast, provides very exact morphological information, and does not involve ionizing radiation compared to PET/CT. MRI is widely used for diagnosing and characterizing pathologies in all regions of the body. The use of multiple receiver channels and parallel imaging enables examination of the whole body with shorter acquisition time while high image quality is maintained. This article gives an overview of initial clinical results obtained with whole-body MRI in staging lung cancer.

For patients with early stage non-small cell lung cancer (NSCLC) unsuitable for resection local high-dose radiotherapy is the treatment of choice. In modern series even with escalated conformal radiotherapy local control rates of about 55% remain disappointing. Within the last years, stereotactic radiotherapy has been shown an effective treatment approach for early stage malignant lung tumors, combining the accurate focal dose delivery by stereotactic techniques with the biological advantages of dose escalated hypofractionated radiotherapy. Typical treatment regimens include three to five fractions over 1-2 weeks or 1 single fraction as radiosurgery. With adequate staging procedures including FDG-PET-CT scan and a low probability of subclinical involvement of unsuspicious locoregional lymph nodes, the concept is to irradiate the primary T1/2 tumor alone. Recent data report local control rates of up to 90%, with favorable results especially for patients in good general condition. Less than 10% of all patients develop isolated tumor recurrences in regional lymph nodes. Three-year survival is significantly improved to more than 80% when biological effective doses of more than 100 Gy are applied to patients in good conditions. Systemic tumor recurrence still is a major problem, making an additional systemic chemotherapy interesting for selected patients after hSRT, such as those younger than 75 years.