Purpose

This study reports clinical experience using a linear accelerator-based MV-kV imaging system for intrafraction motion management during prostate stereotactic body radiation therapy (SBRT).

Methods and Materials

From June 2016 to August 2018, 193 prostate SBRT patients were treated using MV-kV motion management (median dose 40 Gy in 5 fractions). Patients had 3 fiducials implanted then simulated and treated with a full bladder and empty rectum. Pretreatment orthogonal kVs and cone beam computed tomography were used to position patients and evaluate internal anatomy. Motion was tracked during volumetric modulated arc therapy delivery using simultaneously acquired kV and MV images from standard on-board systems. Treatment was interrupted to reposition patients when motion >1.5-2 mm was detected. Motion traces were analyzed and compared with Calypso traces from a previously treated similar patient cohort. To evaluate “natural motion” (ie, if we had not interrupted treatment and repositioned), intrafraction couch corrections were removed from all traces. Clinical effectiveness of the MV-kV system was explored by evaluating toxicity (Common Terminology Criteria for Adverse Events v3.0) and biochemical recurrence rates (nadir + 2 ng/mL).

Results

Median number of interruptions for patient repositioning was 1 per fraction (range, 0-9). Median overall treatment time was 8.2 minutes (range, 4.2-44.8 minutes). Predominant motion was inferior and posterior, and probability of motion increased with time. Natural motion >3 mm and >5 mm in any direction was observed in 32.3% and 10.2% of fractions, respectively. Calypso monitoring (n = 50) demonstrated similar motion results. In the 151 MV-kV patients with ≥3-month follow-up (median, 9.5 months; range, 3-26.5 months), grade ≥2 acute genitourinary/gastrointestinal and late genitourinary/gastrointestinal toxicity was observed in 9.9%/2.0% and 11.9%/2.7%, respectively. Biochemical control was 99.3% with a single failure in a high-risk patient.

Conclusions

The MV-kV system is an effective method to manage intrafraction prostate motion during SBRT, offering the opportunity to correct for prostate clinical target volume displacements that would have otherwise extended beyond typical planning target volume margins.

中文翻译：

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使用基于新型线性加速器的 MV-kV 成像方法进行分次内运动管理的前列腺 SBRT。

目的

本研究报告了在前列腺立体定向放射治疗 (SBRT) 期间使用基于直线加速器的 MV-kV 成像系统进行分次内运动管理的临床经验。

方法和材料

2016 年 6 月至 2018 年 8 月，193 名前列腺 SBRT 患者使用 MV-kV 运动管理（中位剂量 40 Gy，分 5 次）进行治疗。患者植入了 3 个基准点，然后模拟并用充满膀胱和空直肠进行治疗。预处理正交 kV 和锥形束计算机断层扫描用于定位患者并评估内部解剖结构。使用从标准机载系统同时获取的 kV 和 MV 图像，在体积调制电弧治疗期间跟踪运动。当检测到运动 > 1.5-2 mm 时，中断治疗以重新定位患者。对运动轨迹进行分析，并将其与来自先前治疗过的类似患者队列的 Calypso 轨迹进行比较。为了评估“自然运动”（即，如果我们没有中断治疗并重新定位），从所有痕迹中删除了分次内床校正。

结果

患者重新定位中断的中位数为每分 1 次（范围，0-9）。中位总治疗时间为 8.2 分钟（范围为 4.2-44.8 分钟）。主要运动是下位和后位，运动概率随时间增加。分别在 32.3% 和 10.2% 的分数中观察到在任何方向上的自然运动 >3 mm 和 >5 mm。Calypso 监测 (n = 50) 展示了类似的运动结果。在 151 名随访≥3 个月（中位数，9.5 个月；范围，3-26.5 个月）的 MV-kV 患者中，9.9%/2.0% 观察到≥2 级急性泌尿生殖器/胃肠道和晚期泌尿生殖器/胃肠道毒性和 11.9%/2.7%，分别。生化控制率为 99.3%，高危患者一次失败。

结论

MV-kV 系统是在 SBRT 期间管理分次内前列腺运动的有效方法，提供了纠正前列腺临床目标体积位移的机会，否则这些位移将超出典型的计划目标体积边界。