School of Medicine and Public Health, University of Newcastle, Callaghan, NSW, Australia.
Department of Radiation Oncology, Calvary Mater Newcastle, Waratah, NSW, Australia.
Radiat Oncol. 2018 May 18;13(1):97. doi: 10.1186/s13014-018-1033-y.
While intensity modulated radiotherapy (IMRT) has been widely adopted for the treatment of anal cancer (AC), the added contour complexity poses potential risks. This study investigates the impact of contour variation on tumour control probability (TCP) when using IMRT for AC.
Nine Australian centres contoured a single computed tomography dataset of a patient with AC. The same optimised template-based IMRT planning protocol was applied to each contour set to generate nine representative treatment plans and their corresponding dose volume histograms. A geometric analysis was performed on all contours. The TCP was calculated for each plan using the linear quadratic and logitEUD model.
The median concordance index (CI) for the bladder, head and neck of femur, bone marrow, small bowel and external genitalia was 0.94, 0.88, 0.84, 0.65 and 0.65, respectively. The median CI for the involved nodal, primary tumour and elective clinical target volumes were 0.85, 0.77 and 0.71, respectively. Across the nine plans, the TCP was not significantly different. Variation in TCP between plans increased as tumour cell load increased or radiation dose decreased.
When using IMRT for AC, contour variations generated from a common protocol within the limits of minor deviations do not appear to have a significant impact on TCP. Contouring variations may be more critical with increasing tumour cell load or reducing radiotherapy dose.
调强放疗（IMRT）已广泛应用于肛门癌（AC）的治疗，但增加的轮廓复杂性带来了潜在的风险。本研究旨在探讨在使用 IMRT 治疗 AC 时，轮廓变化对肿瘤控制概率（TCP）的影响。
9 个澳大利亚中心对一位 AC 患者的单一 CT 数据集进行了勾画。对每个轮廓集应用相同的优化模板化 IMRT 计划方案，生成 9 个代表性的治疗计划及其相应的剂量体积直方图。对所有轮廓进行几何分析。使用线性二次和对数 EUD 模型计算每个计划的 TCP。
膀胱、股骨头、骨髓、小肠和外生殖器的中位一致性指数（CI）分别为 0.94、0.88、0.84、0.65 和 0.65。受累淋巴结、原发肿瘤和选择性临床靶区的中位 CI 分别为 0.85、0.77 和 0.71。在 9 个计划中，TCP 没有显著差异。TCP 随肿瘤细胞负荷增加或辐射剂量降低而变化。
在使用 IMRT 治疗 AC 时，在较小偏差范围内使用共同方案生成的轮廓变化似乎对 TCP 没有显著影响。随着肿瘤细胞负荷增加或放疗剂量降低，轮廓变化可能更为关键。
