Hedrick Samantha G, Fagundes Marcio, Case Sara, Renegar Jackson, Blakey Marc, Artz Mark, Chen Hao, Robison Ben, Schreuder Niek
Provision Center for Proton Therapy, Knoxville, TN, USA.
J Appl Clin Med Phys. 2017 Jan;18(1):82-89. doi: 10.1002/acm2.12010. Epub 2016 Nov 30.
The purpose of this study was to investigate the consistency of rectal sparing using multiple periodic quality assurance computerized tomography imaging scans (QACT) obtained during the course of proton therapy for patients with prostate cancer treated with a hydrogel spacer. Forty-one low- and intermediate-risk prostate cancer patients treated with image-guided proton therapy with rectal spacer hydrogel were analyzed. To assess the reproducibility of rectal sparing with the hydrogel spacer, three to four QACTs were performed for each patient on day 1 and during weeks 1, 3, and 5 of treatment. The treatment plan was calculated on the QACT and the rectum V90%, V75%, V65%, V50%, and V40% were evaluated. For the retrospective analysis, we evaluated each QACT and compared it to the corresponding treatment planning CT (TPCT), to determine the average change in rectum DVH points. We were also interested in how many patients exceeded an upper rectum V90% threshold on a QACT. Finally, we were interested in a correlation between rectum volume and V90%. On each QACT, if the rectum V90% exceeded the upper threshold of 6%, the attending physician was notified and the patient was typically prescribed additional stool softeners or laxatives and reminded of dietary compliance. In all cases of the rectum V90% exceeding the threshold, the patient had increased gas and/or stool, compared to the TPCT. On average, the rectum V90% calculated on the QACT was 0.81% higher than that calculated on the TPCT. The average increase in V75%, V65%, V50%, and V40% on the QACT was 1.38%, 1.59%, 1.87%, and 2.17%, respectively. The rectum V90% was within ± 1% of the treatment planning dose in 71.2% of the QACTs, and within ± 5% in 93.2% of the QACTs. The 6% threshold for rectum V90% was exceeded in 7 out of 144 QACTs (4.8%), identified in 5 of the 41 patients. We evaluated the average rectum V90% across all QACTs for each of these patients, and it was found that the rectum V90% never exceeded 6%. 53% of the QACTs had a rectum volume within 5 cm of the TPCT volume, 68% were within 10 cm. We found that patients who exceeded the threshold on one or more QACTs had a lower TPCT rectal volume than the overall average. By extrapolating patient anatomy from three to four QACT scans, we have shown that the use of hydrogel in conjunction with our patient diet program and use of stool softeners is effective in achieving consistent rectal sparing in patients undergoing proton therapy.
本研究的目的是通过在接受水凝胶间隔物治疗的前列腺癌患者质子治疗过程中获得的多次定期质量保证计算机断层扫描成像（QACT），来研究直肠保留的一致性。分析了41例接受图像引导质子治疗并使用直肠间隔水凝胶的低危和中危前列腺癌患者。为了评估水凝胶间隔物直肠保留的可重复性，在治疗第1天以及治疗的第1、3和5周，对每位患者进行了三到四次QACT。根据QACT计算治疗计划，并评估直肠的V90%、V75%、V65%、V50%和V40%。对于回顾性分析，我们评估了每次QACT，并将其与相应的治疗计划CT（TPCT）进行比较，以确定直肠剂量体积直方图（DVH）点的平均变化。我们还关注有多少患者在QACT上超过了直肠V90%的上限阈值。最后，我们关注直肠体积与V90%之间的相关性。在每次QACT上，如果直肠V90%超过6%的上限阈值，会通知主治医生，通常会给患者开额外的大便软化剂或泻药，并提醒其遵守饮食规定。在所有直肠V90%超过阈值的病例中，与TPCT相比，患者的气体和/或粪便有所增加。平均而言，QACT上计算的直肠V90%比TPCT上计算的高0.81%。QACT上V75%、V65%、V50%和V40%的平均增加分别为1.38%、1.59%、1.87%和2.17%。在71.2%的QACT中，直肠V90%在治疗计划剂量的±1%范围内，在93.2%的QACT中在±5%范围内。在144次QACT中的7次（4.8%）超过了直肠V90%的6%阈值，这在41例患者中的5例中被发现。我们评估了这些患者每次QACT的平均直肠V90%，发现直肠V90%从未超过6%。53%的QACT直肠体积与TPCT体积相差在5厘米以内，68%在10厘米以内。我们发现，在一次或多次QACT上超过阈值的患者，其TPCT直肠体积低于总体平均值。通过从三到四次QACT扫描推断患者的解剖结构，我们表明，将水凝胶与我们的患者饮食计划以及大便软化剂的使用相结合，对于接受质子治疗的患者实现一致的直肠保留是有效的。
