器官运动和控制对肿瘤放射治疗的影响

放射治疗在肿瘤治疗中占有重要地位，但由于器官运动的影响使肿瘤靶区的精确定位存在一定困难。了解不同器官的运动规律并对其进行控制可有效减小受照体积，保护正常组织。现综述近年来不同器官的运动规律及其控制方法的研究进展。     

肿瘤放射治疗对中枢神经系统的损害

肿瘤放射治疗可引起脑、脊髓和脑血管的损伤,并可诱发脑瘤.本文对这些损害的发病机理、病理改变、临床表现、辅助检查、治疗和预后等作一综述.     

头颈部肿瘤放射治疗新进展

临床肿瘤放射治疗进展 晚期头颈部肿瘤目前治疗上仍然存在着局部控制率低,疗后局部复发率高的缺点,因此如何进一步提高晚期头颈部肿瘤的局部控制率就成为改善预后的关键因素。通过超分割或加速分割技术,或通过化学治疗与放射治疗的配合,以及一些放疗新技术、新方法的应用,可望克服常规分割放疗的缺陷,从而相应改进头颈部肿瘤常规分割放疗的局部控制率。１　　非常规分割照射的研究 主要分为以下几种：（１）加速分割,治疗总时间中度缩短至３３～４０天,而总剂量不变;（２）加速超分割,治疗总时间缩短至１７～３３天,但总剂量相应…     

放射治疗肿瘤新进展

近年来，在高科技发展带动下，适形治疗技术迅速成熟，高传能线密度，临床应用日益活跃。可以预言，这些治疗手段革命性突破将在下个世纪成为癌症的标准治疗方法之一。一、适形治疗适形治疗是一种放射治疗技术。适形，即高放射剂量区（照射野）形态与肿瘤（靶区）形态一致。由于靶区是立体的，且又是用放射线治疗，故称三维适形放射治疗。当靶区体积较小，单次大剂量照射就可达到局部控制目的，该照射方式称为放射外科，其代表产品是伽玛刀。当要求造形治疗靶区内及靶表面剂量分布均匀，则每个照射野内剂量须能按要求调整，并使靶区高剂量，…     

腹部肿瘤的放射治疗—— 肝细胞癌的放射治疗

放疗是肿瘤综合治疗中的重要手段之一,有60%的肿瘤患者在其病程的某一阶段需要放疗。腹部肿瘤占全身所有肿瘤的55%以上,其中尤以胃癌、肝癌位居各种恶性肿瘤的前1、2位。由于放疗设备的进步、放射生物学理论的发展和临床试验的证实,目前,放疗在腹部恶性肿瘤的综合治疗中已显示出作用,作为术后辅助放疗减少复发率,或对不能手术切除患者延长其生存期,或缓解患者的症状。 放疗是腹部肿瘤综合治疗不可缺少的一部分,目前已得到临床肿瘤学家的认可。复旦大学附属中山医院在肝癌放疗领域具有优势,其泌尿系统肿瘤也有不少新内容,胃癌的放疗也积累许多经验。中山医院放疗科依托综合性医院的优势,总结了近年来这些肿瘤的放疗经验。以前的放疗主要是肿瘤专科医院的特长,但随着综合性医院放疗的发展,综合性医院的肿瘤病种主要集中在胸腹部,故本专题对综合性医院放疗科和肿瘤外科医生认识腹部肿瘤的综合治疗具有重要意义。鉴于篇幅有限,如读者感兴趣,可以参考复旦大学附属中山医院放疗科新近出版的《腹盆部肿瘤放射治疗学》。[编者按]     

食管癌大体肿瘤体积对放射治疗近期疗效影响

[目的]观察食管癌大体肿瘤体积(GTV)大小对放射治疗近期疗效的影响.[方法]2000年4月至2002年12月43例食管癌病人采用CT模拟定位及三维TPS设计放疗计划,所有病例均用6MVX线照射,剂量DT50Gy～70Gy/25～35次/5～7周.通过TPS测算每例病人GTV大小及相应的GTV长径、左右径和前后径;X线评价治疗结束时结果;分析GTV及各径线与食管癌近期疗效的关系.[结果]GTV大小20.0cm3、20.1cm3～50.ocm3、＞50.0cm33组的食管癌近期疗效为1级、2级、3 4级分别占55.3%、40.0%和6.7%;12.5%、50.0%和37.5%;8.3%、25.0%和6.7%,各组之间有显著性差异(χ2=14.99,P=0.0047).GTV最大左右径3.ocm3、3.1cm3～4.0cm3、＞4.0cm33组的近期疗效为1级、2级、3 4级分别占44.4%、55.6%和0;33.3%、41.7%和25.0%;13.6%、31.7%和54.6%,各组有显著性差异(χ2=12.38,P=0.015).GTV长径大小与近期疗效有一定关系,但差异无显著性(χ2=4.62,P=0.33).[结论]食管癌GTV大小及左右径对放疗近期疗效的影响有显著性差异,GTV、左右径越大,近期疗效越差.     

肿瘤的放射治疗走向未来

中国恶性肿瘤放射治疗的历史从１９３１年在上海开始,当时唯一专业的放疗科就是现在的上海医科大学肿瘤医院的前身,中比镭锭治疗院。后来虽然有了北京的协和医院及广州的中山医院,但都是放射诊断科下的放射治疗组。从全国来讲,在大城市里的放射治疗单位都有比较先进的...     

肿瘤立体放射治疗的生物学基础

立体放射治疗的目的是使高剂量区剂量分布于肿瘤区域,同时减少肿瘤周围正常组织的受量,提高局限性肿瘤的控制率,减少正常组织并发症。提高局部肿瘤的控制可以减少某些肿瘤的远处转移率,改善肿瘤病人的生存率。因此,立体放射治疗技术将成为今后放射治疗技术发展的主要方向。     

The impact of organ motion on intestine doses and complication probabilities in radiotherapy of bladder cancer.

BACKGROUND AND PURPOSE: The intestine is an organ at risk during irradiation of tumours in the abdomen and pelvis, and it is therefore of interest to predict the risk for complications when planning the treatment. However, this organ displays considerable temporal variations in volume and shape. The aim of this investigation was to investigate the uncertainties caused by organ motion in dose-volume histograms (DVHs) and normal-tissue-complication probabilities (NTCP's). PATIENTS AND METHODS: Between 6 and 8 weekly repeat CT scans were acquired for 10 patients with muscle invading urinary bladder cancer. The intestine was delineated in all scans, and the coordinates of the outlines were transferred to the planning CT using the appropriate transformation. Using the actual treatment plan, the DVHs for each of these 6-8 instances of the intestine as well as the corresponding NTCP estimates were calculated. Also, for each patient, a 3D matrix was created that contained the number of scans where the intestine occupied the voxels represented by the elements of the matrix. From this matrix additional information about the organ movements were extracted. RESULTS: The mean values (across scans for individual patients) for the volume receiving at least 30.8 Gy, V30.8, ranged from 77 to 336 cm3, from 52 to 250 cm3 for V49.5 and from 38 to 243 cm3 for V53.5. The corresponding relative standard deviations were 0.45, 0.45, and 0.51, respectively. The relative standard deviations (over repeat scans for each patient) had ranges 0.065-0.45, 0.10-0.53, and 0.10-0.54 and the mean relative deviations were 0.20, 0.24, and 0.26, approximately half the magnitude of the variation between the mean values for the patients. For 6 out of 10 patients, the volume occupied by the intestine in only one of the CT scans was larger than the volume occupied in all CT scans, thus illustrating the very mobile nature of this organ. CONCLUSIONS: The movements of the small intestine cause large uncertainties in the DVH and calculated NTCP for the individual patient, and the usefulness of dose constraints for this organ may be questioned. Still, the inter-patient variation was larger, and it may be that the DVH can be useful for judging which patients have the greatest risk for radiation injury.     

Analysis and evaluation of periodic physiological organ motion in radiotherapy treatments.

BACKGROUND AND PURPOSE: A system for the detection, measurement and analysis of the periodic physiological organ motion during radiotherapy treatment is proposed and clinically tested in this paper. MATERIAL AND METHODS: The procedure is based on the acquisition of fluoroscopic sequences, followed by an automatic detection of the movement using cross-correlations with matched filters. RESULTS: The system generates a probability density function (PDF) of finding a mobile organ in a position at a certain time. The maximum path of the mobile structures can be determined to define the planning target volume (PTV) without ambiguities. CONCLUSIONS: Physiological movements can be accurately included in the daily planning routine, which is not essentially modified, without needing previous patient training.     

精确放疗中的肿瘤移位及控制方法

肿瘤移位能造成靶区剂量的降低和周围正常组织不必要的照射,是影响放疗精确性的重要因素.研究发现很多胸腹部肿瘤在放疗中都存在移位,导致其移位的主要原因是呼吸运动,目前有多种方法 可以对肿瘤移位加以控制.在精确放疗过程中通过对其加以适当引导和控制以减小不良影响,放射治疗的精确度能得到更进一步的提高.     

Influence of organ motion on conformal vs. intensity-modulated pelvic radiotherapy for prostate cancer

PURPOSE: To compare an intensity-modulated radiotherapy (IMRT) planning approach for prostate pelvic RT with a conformal RT (CRT) approach taking into account the influence of organ-at-risk (OAR) motion. METHODS AND MATERIALS: A total of 20 male patients, each with one planning computed tomography scan and five to eight treatment computed tomography scans, were used for simulation of IMRT and CRT for delivery of a prescribed dose of 50 Gy to the prostate, seminal vesicles, and pelvic lymph nodes. Planning was done in Eclipse without correcting for OAR motion. Evaluation was performed using the CRT and IMRT dose matrices and the planning and treatment OAR outlines. The generalized equivalent uniform dose (gEUD) was calculated for 894 OAR volumes using a volume-effect parameter of 4, 12, and 8 for bowel, rectum and bladder, respectively. For the bowel, the gEUD was normalized to a reference volume of 200 cm(3). For each patient and each OAR, an average of the treatment gEUDs (gEUD(treat)) was calculated for CRT and IMRT. The paired t test was used to compare IMRT with CRT and gEUD(treat) with gEUD(plan). RESULTS: The mean gEUD(treat) was reduced from 43 to 40 Gy, 47 to 46 Gy, and 48 to 45 Gy with IMRT for the bowel, rectum, and bladder, respectively (p < 0.001). Differences between the gEUD(plan) and gEUD(treat) were not significant (p > 0.05) for any OAR but was >6% for the bowel in 6 of 20 patients. CONCLUSION: Intensity-modulated RT reduced the bowel, rectum, and bladder gEUDs also under influence of OAR motion. Neither CRT nor IMRT was robust against bowel motion, but IMRT was not less robust than CRT.     

Optic nerve motion and gaze direction: Their impact on intraorbital tumor radiotherapy

PurposeManagement of inter- and intra-fraction movements of target volumes and organs at risk (OARs) during radiotherapy is essential. While there is little OAR or target volume movement, the movements and orientation of the eyes can be significant during radiotherapy and they can affect the position of the optic nerve. The objective of the present study was to assess the variations of the optic nerve position due to gaze direction and to discuss their clinical consequences on the radiation treatment of intraorbital tumors.Material and methodsThree patients without a history of oculomotor nerve palsy underwent six CT acquisitions with a thermoplastic mask: eyes open with different gaze directions (straight ahead, left, right, up, down) and eyes closed. The acquisition with the straight-ahead gaze was chosen as the reference position. Left and right optic nerves were segmented on the six acquisitions, and total volumes and maximum amplitude motions were calculated in three dimensions.ResultsMaximum differences were observed while looking left and up, with a median maximum amplitude of 5 and 6 mm [range: 2–7 mm], respectively. These motions induced a position variation of more than 50% of the volume of the optic nerve (compared to the reference position). Greater variations of motion were observed for the anterior portion of the nerve. The gaze position with the fewest variations compared to the reference position was eyes closed.ConclusionOptic nerve positions vary significantly due to the gaze direction, especially for the anterior portion of the nerve. These variations should be taken into account for the treatment of small intraorbital tumors involving the anterior third of the optic nerve.     

模拟呼吸运动对肿瘤三维技术放疗的剂量分布影响

目的 通过模拟呼吸运动研究呼吸运动对三维技术放疗剂量分布的影响。方法 对11例肺癌患者进行三维技术放疗计划设计,将二维半导体阵列Mapcheck放在呼吸模拟运动平板3 cm等效水模上,使用近似呼吸运动周期为3.5 s,运动幅度分别为±3、±5、±10、±15 mm,比较运动和静止状态下Mapcheck实测的剂量分布和治疗计划系统输出的相应平面剂量分布。两组数据行配对t检验。结果 呼吸运动均能降低靶区剂量分布的适形度,剂量分布产生模糊效应;11例患者呼吸运动状态下,3DCRT-QA的γ通过率平均值(3%/3 mm)均大于动态IMRT-QA的,且相互比较的P均<0.05;通过Mapcheck系统分析出呼吸运动对3DCRT剂量分布的影响主要集中在靶区周边,可对动态IMRT的影响分布于整个靶区。结论 对呼吸运动幅度较大的肿瘤建议采用3DCRT技术,更能确保运动的肿瘤得到预期较准确的剂量分布,若采用IMRT技术应根据情况对运动肿瘤进行呼吸运动补偿等方法以确保肿瘤相对静止。     

Low hemoglobin levels: influence on tumor biology and radiotherapy treatment outcome

Anemia promotes intratumoral hypoxia, and in turn, hypoxia may adversely impact treatment outcomes by reducing the effectiveness of radiation therapy and by promoting molecular and cellular changes that favor malignant progression and formation of metastases. Recent experimental and clinical studies have been aimed at further exploring the mechanisms by which anemia and hypoxia exert their negative influence in order to identify the more effective interventions to improve clinical prognosis and outcomes. In a recent study of patients with squamous cell carcinoma of the oral cavity and oropharynx, pretreatment hemoglobin (Hb) level and epoetin alfa therapy were independent prognostic factors for response to radiochemotherapy and locoregional tumor control (P <0.01). Patients with pretreatment Hb levels ⩾14.5 g/dl had significantly (P ⩽0.001–P <0.05) higher complete response, 2-year locoregional control, and 2-year survival rates than patients with Hb levels <14.5 g/dl who had not received epoetin alfa. Further, the response, locoregional control, and survival rates of epoetin alfa–treated patients with a pretreatment Hb <14.5 g/dl were significantly higher than those of patients with pretreatment Hb levels <14.5 g/dl not given epoetin alfa, and were equivalent to those of patients with a pretreatment Hb level ⩾14.5 g/dl. These observations and those of several other studies suggest that stabilization of normal Hb levels and correction of treatment-related anemia may contribute to improved therapeutic outcomes in cancer patients. Controlled prospective clinical trials in larger numbers of cancer patients are clearly warranted.     

Strategy for online correction of rotational organ motion for intensity-modulated radiotherapy of prostate cancer

PURPOSE: To develop and evaluate a correction strategy for prostate rotation using gantry and collimator angle adjustments. METHODS AND MATERIALS: Gantry and collimator angle adjustments were used to correct for prostate rotation without rotating the table. A formula to partially correct for left-right (LR) rotations was derived through geometric analysis of rotation-induced clinical target volume (CTV) beam's-eye-view shape changes. For 10 prostate patients, intensity-modulated radiotherapy (IMRT) plans with different margins were created. Simulating CTV LR rotation and correcting each beam by a collimator rotation, the corrected CTV dose was compared with the original and uncorrected dose. Effects of residual geometric uncertainties were assessed using a Monte Carlo technique. A large number of treatments representative for prostate patients were simulated. Dose probability histograms of the minimum CTV dose (D min) were derived, with and without online correction, resulting in a more realistic margin estimate. RESULTS: Dosimetric analysis of all IMRT plans showed that, with rotational correction and a 2-mm margin, D min was constant to within 3% for LR rotations up to +/-15 degrees . The Monte Carlo dose probability histograms showed that, with correction, a margin of 4 mm ensured that 90% of patients received a D min >or=95% of the prescribed dose. Without correction a margin of 6 mm was required. CONCLUSIONS: We developed and tested a practical method for (online) correction of prostate rotation, allowing safe and straightforward implementation of margin reduction and dose escalation.