Chilukuri Srinivas, Sundar Sham, Patro Kartikeswar, Sawant Mayur, Sivaraman Rangasamy, Arjunan Manikandan, Panda Pankaj Kumar, Sharma Dayananda, Jalali Rakesh
Department of Radiation Oncology, Apollo Proton Cancer Centre, Chennai, India.
Int J Part Ther. 2022 Jun 13;9(1):42-53. doi: 10.14338/IJPT-21-00042.1. eCollection 2022 Summer.
To compare the late gastrointestinal (GI) and genitourinary toxicities (GU) estimated using multivariable normal tissue complication probability (NTCP) models, between pencil-beam scanning proton beam therapy (PBT) and helical tomotherapy (HT) in patients of high-risk prostate cancers requiring pelvic nodal irradiation (PNI) using moderately hypofractionated regimen.
Twelve consecutive patients treated with PBT at our center were replanned with HT using the same planning goals. Six late GI and GU toxicity domains (stool frequency, rectal bleeding, fecal incontinence, dysuria, urinary incontinence, and hematuria) were estimated based on the published multivariable NTCP models. The ΔNTCP (difference in absolute NTCP between HT and PBT plans) for each of the toxicity domains was calculated. A one-sample Kolmogorov-Smirnov test was used to analyze distribution of data, and either a paired test or a Wilcoxon matched-pair signed rank test was used to test statistical significance.
Proton beam therapy and HT plans achieved adequate target coverage. Proton beam therapy plans led to significantly better sparing of bladder, rectum, and bowel bag especially in the intermediate range of 15 to 40 Gy, whereas doses to penile bulb and femoral heads were higher with PBT plans. The average ΔNTCP for grade (G)2 rectal bleeding, fecal incontinence, stool frequency, dysuria, urinary incontinence, and G1 hematuria was 12.17%, 1.67%, 2%, 5.83%, 2.42%, and 3.91%, respectively, favoring PBT plans. The average cumulative ΔNTCP for GI and GU toxicities (ΣΔNTCP) was 16.58% and 11.41%, respectively, favoring PBT. Using a model-based selection threshold of any G2 ΔNTCP >10%, 67% (8 patients) would be eligible for PBT.
Proton beam therapy plans led to superior sparing of organs at risk compared with HT, which translated to lower NTCP for late moderate GI and GU toxicities in patients of prostate cancer treated with PNI. For two-thirds of our patients, the difference in estimated absolute NTCP values between PBT and HT crossed the accepted threshold for minimal clinically important difference.
比较在采用适度低分割方案进行盆腔淋巴结照射（PNI）的高危前列腺癌患者中，使用多变量正常组织并发症概率（NTCP）模型估计的笔形束扫描质子束治疗（PBT）与螺旋断层放疗（HT）之间的晚期胃肠道（GI）和泌尿生殖系统毒性（GU）。
对在我们中心接受PBT治疗的12例连续患者，使用相同的计划目标重新进行HT计划。基于已发表的多变量NTCP模型估计6个晚期GI和GU毒性领域（大便频率、直肠出血、大便失禁、排尿困难、尿失禁和血尿）。计算每个毒性领域的ΔNTCP（HT和PBT计划之间绝对NTCP的差异）。使用单样本柯尔莫哥洛夫-斯米尔诺夫检验分析数据分布，并使用配对t检验或威尔科克森配对符号秩检验检验统计学显著性。
质子束治疗和HT计划实现了足够的靶区覆盖。质子束治疗计划尤其在15至40 Gy的中间剂量范围内，能显著更好地保护膀胱、直肠和肠袋，而PBT计划对阴茎球部和股骨头的剂量更高。2级直肠出血、大便失禁、大便频率、排尿困难、尿失禁和1级血尿的平均ΔNTCP分别为12.17%、1.67%、2%、5.83%、2.42%和3.91%，更有利于PBT计划。GI和GU毒性的平均累积ΔNTCP（ΣΔNTCP）分别为16.58%和11.41%，更有利于PBT。使用基于模型的选择阈值，即任何G2 ΔNTCP>10%，67%（8例患者）符合PBT条件。
与HT相比，质子束治疗计划能更好地保护危及器官，这转化为接受PNI治疗的前列腺癌患者晚期中度GI和GU毒性的NTCP更低。对于我们三分之二的患者，PBT和HT之间估计绝对NTCP值的差异超过了最小临床重要差异的公认阈值。
