Bucknell Nicholas, Hardcastle Nicholas, Gunewardena Roshini, Nguyen Long, Callahan Jason, Ball David, Selbie Lisa, Kron Tomas, Turgeon Guy-Anne, Hofman Michael S, Siva Shankar
Department of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, Australia.
Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Australia.
Clin Transl Radiat Oncol. 2023 Feb 15;40:100599. doi: 10.1016/j.ctro.2023.100599. eCollection 2023 May.
Four-Dimensional Gallium 68 Ventilation-Perfusion Positron Emission Tomography (Ga-4D-V/Q PET/CT) allows for dynamic imaging of lung function. To date there has been no assessment of the feasibility of adapting radiation therapy plans to changes in lung function imaged at mid-treatment function using Ga-4D-V/Q PET/CT. This study assessed the potential reductions of dose to the functional lung when radiation therapy plans were adapted to avoid functional lung at the mid-treatment timepoint using volumetric arc radiotherapy (VMAT).
A prospective clinical trial (U1111-1138-4421) was performed in patients undergoing conventionally fractionated radiation therapy for non-small cell lung cancer (NSCLC). A Ga-4D-V/Q PET/CT was acquired at baseline and in the 4th week of treatment. Functional lung target volumes using the ventilated and perfused lung were created. Baseline functional volumes were compared to the week 4 V/Q functional volumes to describe the change in function over time. For each patient, 3 VMAT plans were created and optimised to spare ventilated, perfused or anatomical lung. All key dosimetry metrics were then compared including dose to target volumes, dose to organs at risk and dose to the anatomical and functional sub-units of lung.
25 patients had both baseline and 4 week mid treatment Ga-4D-V/Q PET/CT imaging. This resulted in a total of 75 adapted VMAT plans. The volume decreased in 16/25 patients with a mean of the change in volume (cc) -28 ± 515 cc [±SD, range -996 cc to 1496 cc]. The volume increased in 13/25 patients with mean of the change in volume (cc) + 112 ± 590 cc. [±SD, range -1424 cc to 950 cc]. The functional lung sparing technique was found to be feasible with no significant differences in dose to anatomically defined organs at risk. Most patients did derive a benefit with a reduction in functional volume receiving 20 Gy (fV20) and/or functional mean lung dose (fMLD) in either perfusion and/or ventilation. Patients with the most reduction in fV20 and fMLD were those with stage III NSCLC.
Functional lung volumes change during treatment. Some patients benefit from using Ga-4D-V/Q PET/CT in the 4th week of radiation therapy to adapt radiation plans. In these patients, the role of mid-treatment adaptation requires further prospective investigation.
四维镓68通气灌注正电子发射断层扫描（Ga - 4D - V/Q PET/CT）可对肺功能进行动态成像。迄今为止，尚未评估根据使用Ga - 4D - V/Q PET/CT在治疗中期成像的肺功能变化来调整放射治疗计划的可行性。本研究评估了在使用容积弧形调强放疗（VMAT）时，将放射治疗计划调整为在治疗中期避开功能肺时，对功能肺剂量的潜在降低情况。
对接受非小细胞肺癌（NSCLC）常规分割放射治疗的患者进行了一项前瞻性临床试验（U1111 - 1138 - 4421）。在基线和治疗第4周时进行了Ga - 4D - V/Q PET/CT检查。利用通气和灌注肺创建了功能肺靶区体积。将基线功能体积与第4周的V/Q功能体积进行比较，以描述功能随时间的变化。对于每位患者，创建并优化了3个VMAT计划，以保护通气、灌注或解剖肺。然后比较了所有关键剂量学指标，包括靶区剂量、危及器官剂量以及肺的解剖和功能亚单位剂量。
25例患者在基线和治疗第4周均进行了Ga - 4D - V/Q PET/CT成像。这共产生了75个调整后的VMAT计划。16/25例患者的 体积减小，体积变化均值（cc）为 - 28 ± 515 cc [±标准差，范围 - 996 cc至1496 cc]。13/25例患者的 体积增加，体积变化均值（cc）为 + 112 ± 590 cc [±标准差，范围 - 1424 cc至950 cc]。发现功能肺保护技术是可行的，对解剖学定义的危及器官的剂量无显著差异。大多数患者在灌注和/或通气方面，接受20 Gy（fV20）和/或功能平均肺剂量（fMLD）的功能体积减少，确实从中受益。fV20和fMLD减少最多的患者是III期NSCLC患者。
治疗期间功能肺体积会发生变化。一些患者受益于在放射治疗第4周使用Ga - 4D - V/Q PET/CT来调整放射治疗计划。对于这些患者，治疗中期调整的作用需要进一步的前瞻性研究。
