Mazeron R, Kamsu Kom L, Rivin del Campo E, Dumas I, Farha G, Champoudry J, Chargari C, Martinetti F, Lefkopoulos D, Haie-Meder C
Unité de curiethérapie, département of radiothérapie, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France; Laboratoire de radiothérapie moléculaire, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France; Inserm U1030, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France.
Unité de curiethérapie, département of radiothérapie, institut de cancérologie Gustave-Roussy, 114, rue Édouard-Vaillant, 94805 Villejuif cedex, France.
Cancer Radiother. 2014 Jun;18(3):177-82. doi: 10.1016/j.canrad.2014.03.002. Epub 2014 Apr 21.
The implementation of image-guided brachytherapy in cervical cancer raises the problem of adapting the experience acquired with 2D brachytherapy to this technique. The GEC-ESTRO (Groupe européen de curiethérapie - European Society for Radiotherapy and Oncology) has recommended reporting the dose delivered to the rectum in the maximally exposed 2 cm(3) volume, but so far, the recommended dose constraints still rely on 2D data. The aim of this study was to evaluate the relationship between the doses evaluated at the ICRU rectal point and modern dosimetric parameters.
For each patient, dosimetric parameters were generated prospectively at the time of dosimetry and were reported. For analysis, they were converted in 2 Gy equivalent doses using an α/β ratio of 3 with a half-time of repair of 1.5 hours.
The dosimetric data from 229 consecutive patients treated for locally advanced cervical cancer was analyzed. The mean dose calculated at ICRU point (DICRU) was 55.75 Gy ± 4.15, while it was 59.27 Gy ± 6.16 in the maximally exposed 2 cm(3) of the rectum (P=0.0003). The D2 cm(3) was higher than the DICRU in 78% of the cases. The mean difference between D2 cm(3) and DICRU was 3.53 Gy ± 4.91. This difference represented 5.41% ± 7.40 of the total dose delivered to the rectum (EBRT and BT), and 15.49% ± 24.30 of the dose delivered when considering brachytherapy alone. The two parameters were significantly correlated (P=0.000001), and related by the equation: D2 cm(3)=0.902 × DICRU + 0.984. The r(2) coefficient was 0.369.
In this large cohort of patients, the DICRU significantly underestimates the D2 cm(3). This difference probably results from the optimization process itself, which consists in increasing dwell times above the ICRU point in the cervix. Considering these findings, caution must be taken while implementing image-guided brachytherapy and dose escalation.
宫颈癌图像引导近距离放射治疗的实施引发了如何将二维近距离放射治疗所积累的经验应用于该技术的问题。欧洲近距离放射治疗协作组-欧洲放射治疗与肿瘤学会（GEC-ESTRO）建议报告最大暴露的2 cm³体积内直肠所接受的剂量，但到目前为止，推荐的剂量限制仍依赖二维数据。本研究的目的是评估在国际辐射单位与测量委员会（ICRU）直肠点评估的剂量与现代剂量学参数之间的关系。
对每位患者在剂量测定时前瞻性地生成剂量学参数并进行报告。为进行分析，使用α/β比值为3且修复半衰期为1.5小时将其转换为2 Gy等效剂量。
分析了229例接受局部晚期宫颈癌治疗的连续患者的剂量学数据。在ICRU点计算的平均剂量（DICRU）为55.75 Gy±4.15，而在直肠最大暴露的2 cm³内为59.27 Gy±6.16（P = 0.0003）。在78%的病例中，D2 cm³高于DICRU。D2 cm³与DICRU之间的平均差值为3.53 Gy±4.91。该差值占直肠所接受的总剂量（外照射放疗和近距离放疗）的5.41%±7.40，占仅考虑近距离放疗时所给予剂量的15.49%±24.30。这两个参数显著相关（P = 0.000001），并通过以下方程相关联：D2 cm³ = 0.902×DICRU + 0.984。r²系数为0.369。
在这一大型患者队列中，DICRU显著低估了D2 cm³。这种差异可能源于优化过程本身，该过程包括增加宫颈内ICRU点上方的驻留时间。考虑到这些发现，在实施图像引导近距离放射治疗和剂量递增时必须谨慎。
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