Gandhi Saumil J, Liang Xing, Ding Xuanfeng, Zhu Timothy C, Ben-Josef Edgar, Plastaras John P, Metz James M, Both Stefan, Apisarnthanarax Smith
University of Pennsylvania, Department of Radiation Oncology, Philadelphia, Pennsylvania.
University of Pennsylvania, Department of Radiation Oncology, Philadelphia, Pennsylvania; Currently at University of Washington, Department of Radiation Oncology, Seattle, Washington.
Pract Radiat Oncol. 2015 Jul-Aug;5(4):209-18. doi: 10.1016/j.prro.2015.01.004. Epub 2015 Feb 18.
Stereotactic body radiation therapy (SBRT) for treatment of liver tumors is often limited by liver dose constraints. Protons offer potential for more liver sparing, but clinical situations in which protons may be superior to photons are not well described. We developed and validated a treatment decision model to determine whether liver tumors of certain sizes and locations are more suited for photon versus proton SBRT.
Six spherical mock tumors from 1 to 6 cm in diameter were contoured on computed tomography images of 1 patient at 4 locations: dome, caudal, left medial, and central. Photon and proton plans were generated to deliver 50 Gy in 5 fractions to each tumor and optimized to deliver equivalent target coverage and maximal liver sparing. Using these plans, we developed a hypothesis-generating model to predict the optimal modality for maximal liver sparing based on tumor size and location. We then validated this model in 10 patients with liver tumors.
Protons spared significantly more liver than photons for dome or central tumors ≥3 cm (dome: 134 ± 21 cm(3), P = .03; central: 108 ± 4 cm(3), P = .01). Our model correctly predicted the optimal SBRT modality for all 10 patients. For patients with dome or central tumors ≥3 cm, protons significantly increased the volume of liver spared (176 ± 21 cm(3), P = .01) and decreased the mean liver dose (8.4 vs 12.2 Gy, P = .01) while offering no significant advantage for tumors <3 cm at any location or for caudal and left medial tumors of any size.
When feasible, protons should be considered as the radiation modality of choice for dome and central tumors >3 cm to allow maximal liver sparing and potentially reduce radiation toxicity. Protons should also be considered for any tumor >5 cm if photon plans fail to achieve adequate coverage or exceed the mean liver threshold.
立体定向体部放射治疗（SBRT）用于治疗肝脏肿瘤时，常受肝脏剂量限制。质子治疗有可能更好地保护肝脏，但质子治疗优于光子治疗的临床情况尚未得到充分描述。我们开发并验证了一种治疗决策模型，以确定特定大小和位置的肝脏肿瘤更适合光子还是质子SBRT。
在1例患者的计算机断层扫描图像上，于4个位置勾勒出6个直径为1至6厘米的球形模拟肿瘤：肝顶、肝尾、肝左内侧和肝中央。生成光子和质子计划，将每个肿瘤分5次给予50 Gy剂量，并进行优化以实现等效的靶区覆盖和最大程度的肝脏保护。利用这些计划，我们开发了一个假设生成模型，根据肿瘤大小和位置预测最大程度肝脏保护的最佳治疗方式。然后，我们在10例肝脏肿瘤患者中验证了该模型。
对于直径≥3厘米的肝顶或肝中央肿瘤，质子治疗比光子治疗能显著多保护肝脏（肝顶：134±21立方厘米，P = 0.03；肝中央：108±4立方厘米，P = 0.01）。我们的模型正确预测了所有10例患者的最佳SBRT治疗方式。对于直径≥3厘米的肝顶或肝中央肿瘤患者，质子治疗显著增加了肝脏保护体积（176±21立方厘米，P = 0.01），并降低了肝脏平均剂量（8.4 Gy对12.2 Gy，P = 0.01），而对于任何位置直径<3厘米的肿瘤或任何大小的肝尾和肝左内侧肿瘤，质子治疗没有显著优势。
可行时，对于直径>3厘米的肝顶和肝中央肿瘤，应考虑将质子作为放射治疗的首选方式，以实现最大程度的肝脏保护并可能降低放射毒性。如果光子计划未能实现充分覆盖或超过肝脏平均阈值，对于任何直径>5厘米的肿瘤也应考虑质子治疗。
