RapidArc与Novalis Knife在多发脑转移瘤SRS中的剂量学比较

目的:比较基于多叶准直器的RapidArc与基于圆形限光筒的Novalis Knife在多发脑转移瘤立体定向放射外科（SRS）中的剂量学差异。方法:选取10例已进行Novalis Knife治疗的多发脑转移瘤患者（转移瘤3~5个/人）,共37个转移瘤。重新设计单中心、非共面4弧的RapidArc SRS计划,靶区处方剂量统一为16 Gy。比较Novalis Knife计划和RapidArc SRS计划中靶区的剂量适形度指数和均匀性指数、靶区周围剂量梯度指数、正常脑组织等剂量线体积（V16、V12、V9、V6、V3）以及治疗所需的机器跳数。结果:RapidArc SRS计划相较于Novalis Knife计划,适形度指数更接近于1（0.79[±]0.10 vs 0.50[±]0.22, P=0.000）,均匀性指数更接近于0（0.07[±]0.01 vs 0.15[±]0.07, P=0.000）,但靶区周围剂量梯度指数较大（15.92[±]12.43 vs 5.05[±]3.53, P=0.000）。对于正常脑组织等剂量线体积,RapidArc SRS计划中V16明显小于Novalis Knife计划（P=0.005）;两计划的V12、V9无明显差异（P=0.445, 0.059）;而RapidArc SRS计划中V6、V3明显大于Novalis Knife计划（P=0.005, 0.005）。RapidArc SRS计划的机器跳数明显少于Novalis Knife计划（P=0.005）。结论:RapidArc SRS计划通过设置单一治疗等中心可实现颅内多个转移瘤的同步放射外科治疗,具有更高的靶区剂量适形度及均匀性;但靶区周边剂量跌落陡度不及Novalis Knife计划,正常脑组织低剂量受照范围较大。治疗依从性较差的多发脑转移患者可考虑选择治疗效率更高的RapidArc技术,并根据临床实际情况调整剂量分割模式,以减少放射损伤风险。     

Clinical Analysis of Novalis Stereotactic Radiosurgery for Brain Metastases

Objective

The authors analyzed the effectiveness and therapeutic response of Novalis shaped beam radiosurgery for metastatic brain tumors, and the prognostic factors which influenced the outcome.

Methods

We performed a retrospective analysis of 106 patients who underwent 159 treatments for 640 metastatic brain lesions between January 2000 and April 2008. The pathologies of the primary tumor were mainly lung (45.3%), breast (18.2%) and GI tract (13.2%). We classified the patients using Radiation Therapy Oncology Group Recursive Partitioning Analysis (RPA) and then analyzed the survival and prognostic factors according to the Kaplan Meier method and univariate analysis.

Results

The overall median actuarial survival rate was 7.3 months from the time of first radiosurgery treatment while 1 and 2 year actuarial survival estimates were 31% and 14.4%, respectively. Median actuarial survival rates for RPA classes I, II, and III were 31.3 months, 7.5 months and 1.7 months, respectively. Patients'' life spans, higher Karnofsky performance scores and age correlated closely with RPA classes. However, sex and the number of lesions were not found to be significantly associated with length of survival.

Conclusion

This result suggests that Novalis radiosurgery can be a good treatment option for treatment of the patients with brain metastases.     

Hypofractionated stereotactic body radiation therapy (SBRT) for limited hepatic metastases

PURPOSE: To evaluate the feasibility and efficacy of hypofractionated stereotactic body radiation therapy (SBRT) for the treatment of liver metastases. METHODS AND MATERIALS: The records of 69 patients with 174 metastatic liver lesions treated with SBRT between April 2001 and October 2004 were reviewed. The most common primary tumors were colorectal (n = 20), breast (n = 16), pancreas (n = 9), and lung (n = 5). The mean number of lesions treated per patient was 2.5 (range, 1-6). The longest diameter of the lesions ranged in size from 0.6 to 12.2 cm (median, 2.7 cm). Dose per fraction ranged from 2 Gy to 6 Gy, with a median total dose of 48 Gy (range, 30-55 Gy). Dose was prescribed to the 100% isodose line (IDL), with the 80% IDL covering the gross tumor volume with a minimum margin of 7 mm. RESULTS: The median follow up was 14.5 months. Sixty patients were evaluable for response based on an abdominal computed tomography scan obtained at a minimum of 3 months after completion of SBRT. The actuarial overall infield local control rate of the irradiated lesions was 76% and 57% at 10 and 20 months, respectively. The median overall survival time was 14.5 months. The progression-free survival rate was 46% and 24% at 6 and 12 months, respectively. None of the patients developed Grade 3 or higher toxicity. CONCLUSION: Hypofractionated SBRT provides excellent local control with minimal side effects in selected patients with limited hepatic metastases.     

A review of 3 current radiosurgery systems

BACKGROUND: Stereotactic radiosurgery and fractionated stereotactic radiotherapy have become widespread techniques applied to the treatment of a variety of intracranial lesions. Rapid evolution of new technologies has now enabled clinicians to treat tumors outside the cranium and down the spinal axis. This review compares 3 commercially available systems in widespread use throughout the world. METHODS: Literature review and interviews with practitioners in the United States were performed to establish data for a comparative analysis of the Gamma Knife (Elekta, Sweden), Novalis (BrainLabs, Germany), and CyberKnife systems (Accuray, Sunnyvale, CA). Cost analyses were deliberately excluded because of the need for detailed cost-benefit analysis beyond the scope of the review. RESULTS: An unbiased comparative analysis was not possible because of the lack of objective data from a standard metric for these systems. Despite this shortcoming, disparate features of each system were compared and contrasted. CONCLUSION: A careful assessment of each system, including its operational features, capabilities, and yearly capacity must be weighed against the composition of the radiosurgery team, the case mix of the practice, and the objectives of the clinical unit to yield the best fit.     

Traitement des métastases cérébrales par radiochirurgie stéréotaxique : étude de 33 cas liés à un accident de « surexposition »

The consequences of a dosimetric radiosurgery accident are not the same as a conventional radiotherapy accident. The objective of this study was to estimate the clinical and radiological outcome of patients treated by radiosurgery for metastasis during the period of the overexposure accident that occurred in the Toulouse Radiosurgery Unit. Between April 2006 and March 2007, 33 patients with 57 metastases were treated in the Toulouse Radiosurgery Unit (Novalis^®, BrainLab). An initial error in the estimation of the scatter factors led to an overexposure to radiation. The median age was 55 years [range, 35-85]. Twenty-one patients (64%) harbored a single metastasis. The primary tumor location was lung (16 cases), kidney (nine cases), breast (four cases), and others (four cases). The mean tumoral volume was 3.2 cm³ [0.04-14.07]. The mean prescribed dose at the isocenter was 20 Gy [range, 10-23], the mean delivered dose was 31.5 Gy [range, 13-52], and the mean overdose was 61.2% [range, 5.6-226.8]. In order to evaluate the consequences of the overdose, three parameters were analyzed: a risk index using dose and volume, the volume of parenchyma that received more than 12 Gy, and the mean dose in a sphere of 20 cm³ surrounding the target volume. Median actuarial survival was 14.1 months, the survival rate was 79.4 % at six months, 59.1% at 12 months, and 27.2% at 24 months. The rate of tumor control was 80.7%. No morbidity was observed. There was no correlation between death and the parameters studied. The survival rates and times observed in our study of the patients treated for brain metastases by radiosurgery and overexposed were among the good results of the international literature. Deaths were not related to the overdose and no side effect was noted. This dosimetric accident has not had worse consequences in this population.