Raso Roberta, Scalco Elisa, Fiorino Claudio, Broggi Sara, Cattaneo Giovanni Mauro, Garelli Stefania, Pagliazzi Marco, Slim Najla, di Muzio Nadia, Rizzo Giovanna, Calandrino Riccardo, Passoni Paolo
Medical Physics, San Raffaele Scientific Institute, Milano, Italy.
Istituto di Bioimmagini e Fisiologia Molecolare, CNR, Segrate, Milano, Italy.
Phys Med. 2015 Mar;31(2):167-72. doi: 10.1016/j.ejmp.2014.12.002. Epub 2015 Jan 10.
An adaptive concomitant boost (ACB) for the neo-adjuvant treatment of rectal cancer was clinically implemented. In this study population margins M(90,90) considering rectal deformation were derived for 10 consecutive patients treated at 18 × 2.3Gy with Helical Tomotherapy (HT) and prospectively validated on 20 additional patients treated with HT, delivering ACB in the last 6 fractions.
Sectorial margins M(90,90) of the whole and second treatment parts were assessed for 90% population through a method combining the 90% coverage probability maps of rectal positions (CPC90%) with 3D local distance measurements between the CPC90% and a reference rectal contour. M(90,90) were compared with the margins M(90,90)(95%/99%), ensuring CPC90% coverage with 95%/99% confidence level. M(90,90) of the treatment second part were chosen as ACB margins which were clinically validated for each patient by means of %volume missing of CPC5/6 excluded by the ACB margins.
The whole treatment M(90,90) ranged between 1.9 mm and 9 mm in the lower-posterior and upper-anterior sectors, respectively. Regarding ACB, M(90,90) were 7 mm in the anterior direction and <5 mm elsewhere. M(90,90)(95%/99%) did not significantly differ from M(90,90). The %volume excluded by the ACB margin was<2% for all male and <5% for 9/10 female patients. The dosimetry impact on R_adapt for the patients with the largest residual error was negligible.
Local deformation measurements confirm an anisotropic motion of rectum once set-up error is rigidly corrected. Margins of 7 mm anterior and 5 mm elsewhere are adequate for ACB. Female patients show a slightly larger residual error.
临床上实施了一种用于直肠癌新辅助治疗的自适应同期增量照射（ACB）。在本研究人群中，针对连续10例接受螺旋断层放疗（HT）、剂量为18×2.3Gy的患者，得出了考虑直肠变形的边缘M(90,90)，并在前瞻性研究中对另外20例接受HT治疗且在最后6次分割中进行ACB的患者进行了验证。
通过将直肠位置的90%覆盖概率图（CPC90%）与CPC90%和参考直肠轮廓之间的三维局部距离测量相结合的方法，评估了90%人群的整个治疗部分和第二治疗部分的扇形边缘M(90,90)。将M(90,90)与边缘M(90,90)(95%/99%)进行比较，确保在95%/99%置信水平下达到CPC90%覆盖。将治疗第二部分的M(90,90)选为ACB边缘，并通过ACB边缘排除的CPC5/6的体积缺失百分比对每位患者进行临床验证。
整个治疗的M(90,90)在下后和上前扇形区域分别在1.9毫米至9毫米之间。对于ACB，向前方向的M(90,90)为7毫米，其他方向<5毫米。M(90,90)(95%/99%)与M(90,90)无显著差异。所有男性患者ACB边缘排除的体积百分比<2%，9/10的女性患者<5%。对于残留误差最大的患者，剂量学对R_adapt的影响可忽略不计。
一旦严格校正摆位误差，局部变形测量证实直肠存在各向异性运动。向前7毫米和其他方向5毫米的边缘适用于ACB。女性患者显示出稍大的残留误差。
