Improving Pancreas RT Plans using Respiration-driven Anatomic Deformation

描述(申请人提供)：胰腺癌是一种致命的癌症，超过85%的患者出现局部晚期或转移性疾病。目前，局部晚期胰腺癌(LAPC)常规分割放射治疗(RT)的局部失败率为40-70%。当使用25Gy单剂量立体定向全身放射治疗(SBRT)时，无局部进展存活率接近100%，但GI毒性显著，因此需要分次(3-5个部分)的SBRT进行进一步试验。SBRT治疗要求计划满足严格的正常组织限制，而传统的计划策略由于肿瘤和关键器官的密切接近而难以实现。呼吸诱导的器官运动迫使肿瘤周围有很大的边缘，增加了照射的正常组织的体积，从而增加了胃肠道毒性的风险，从而使治疗计划进一步复杂化。显然需要新的治疗计划战略来克服这些问题。目的：收集初步剂量学数据，为一种新的策略收集初步剂量学数据，该策略利用呼吸驱动的解剖变形的“双重实例”方法来改进胰腺治疗计划。长期目标是使用从这项试点拨款中学到的信息来筛查和治疗可能 受益于双实例规划方法。方法：(1)利用磁共振(MR)和计算机断层扫描(CT)成像技术，定量测量患者在深吸气(INSP)和呼气(EXP)时腹部结构的几何运动和变形。(2)使用一种先进的形变图像配准算法来映射INSP和EXP状态之间的失真，从而可以映射和分析治疗计划剂量分布。(3)。使用自由呼吸、仅EXP、仅INSP和EXP和INSP的新型双实例组合来优化计划，以研究在一个或多个这些实例中可以实现的胰腺肿瘤剂量的潜在改善，利用肿瘤和关键器官位置的相对移动。影响：这项初步研究的成功将为在后续临床试验中使用改进的技术(S)奠定必要的基础，该临床试验将在不增加毒性的情况下增加LAPC患者的剂量。

DESCRIPTION (provided by applicant): Pancreatic adenocarcinoma is a lethal cancer, with more than 85% of patients presenting with either locally advanced or metastatic disease. Current treatment of locally advanced pancreatic cancer (LAPC) with regular fractionated radiation therapy (RT) results in local failure rates of 40-70%. While local progression free survival approached 100% when stereotactic body radiation therapy (SBRT) with a single dose of 25 Gy was used, the GI toxicities were significant, thus requiring hypo-fractionated (3 to 5 fraction) SBRT for future trials. SBRT treatment requires plans to satisfy stringent normal tissue constraints that are difficult to achieve with conventional planning strategy due to the close proximity of tumor and critical organs. Treatment planning is further complicated by respiration-induced organ motion which forces large margins around tumor, increasing the volume of the normal tissue irradiated and thus increasing the risk of GI toxicity. New treatment planning strategies are clearly needed to overcome these problems. Goals: To gather preliminary dosimetric data for a novel strategy which makes use of respiration-driven anatomic deformation in a "dual instance" method to improve pancreatic treatment plans. The long-term objective is to use the information learned from this pilot grant to screen and treat patients that can potentially benefit from the Dual Instance planning method. Methods: (1) Use magnetic resonance (MR) and computed tomography (CT) imaging to quantify geometric motions and deformations in abdominal structures as patients hold their breath at deep inspiration (INSP) and expiration (EXP). (2) Use an advanced deformation image registration algorithm to map the distortions between INSP and EXP states, so treatment plan dose distributions can be mapped and analyzed. (3). Optimize plans using free breathing, EXP-only, INSP-only, and a novel dual-instance combination of EXP and INSP to study potential improvements in pancreatic tumor dose which can be achieved in one or more of these instances, taking advantage of relative shifts in tumor and critical organ positions. Impact: Success of this pilot study will lay the groud work necessary for use of the improved technique(s) in the follow-on clinical trials which escalate dose to patients with LAPC without increasing toxicity.