Eminowicz G, Motlib J, Khan S, Perna C, McCormack M
Radiotherapy Department, University College London Hospital, London, UK.
Radiotherapy Department, University College London Hospital, London, UK.
Clin Oncol (R Coll Radiol). 2016 Sep;28(9):e85-91. doi: 10.1016/j.clon.2016.04.044. Epub 2016 May 11.
Minimisation of organ position variation during pelvic radiotherapy is vital for accurate treatment. We analysed bladder and rectal filling during radiotherapy to understand variation reduction methods.
Cone beam computed tomography scans (CBCTs) taken twice weekly during three-dimensional conformal radiotherapy were retrospectively analysed for 10 cervical cancer patients. Bladder and bowel preparation was followed. Two independent clinicians outlined bladder, rectum and the primary clinical target volume (CTV) on each CBCT. Effects of time, chemotherapy and drinking time on bladder and rectal volume were analysed. CTV coverage impact was investigated using fixed effect logistic regression modelling.
Ten planning scans and 109 CBCTs were reviewed. The bladder volume was 45-578 cm(3) during radiotherapy and 73-664 cm(3) at planning. The bladder volume increased (4 cm(3)/min) with waiting time, decreased (average 4 cm(3)/day) through treatment and was larger (about 50 cm(3)) after chemotherapy. A bladder volume difference > 130 cm(3) from planning led to the planning target volume (PTV) not covering the CTV. The probability of the PTV covering the CTV for every cm(3) deviation from the planning volume reduced by 1.9%, predominantly affecting the uterus. Planning bladder volumes > 300 cm(3) were not reproducible during treatment. The rectal anterior-posterior diameter correlated with volume. No pattern was displayed through treatment. The probability of the PTV covering the CTV with every mm deviation from the planning anterior-posterior diameter reduced by 5.8%, predominantly affecting the cervix. The risk of the PTV not covering the CTV is higher if the rectum is larger during treatment than planning. As bladder volume decreased rectal anterior-posterior diameter increased.
Our data suggest an ideal planning bladder volume of 150-300 cm(3), a shorter waiting time on post-chemotherapy days and adequate hydration throughout treatment. Laxatives at planning and throughout treatment may also be beneficial. Even with these measures, regular imaging is vital when implementing advanced radiotherapy techniques for gynaecological cancers.
在盆腔放疗期间将器官位置变化最小化对于精确治疗至关重要。我们分析了放疗期间膀胱和直肠的充盈情况，以了解减少变化的方法。
回顾性分析了10例宫颈癌患者在三维适形放疗期间每周两次进行的锥形束计算机断层扫描（CBCT）。遵循膀胱和肠道准备要求。两名独立的临床医生在每次CBCT上勾勒出膀胱、直肠和主要临床靶区（CTV）。分析了时间、化疗和饮水时间对膀胱和直肠体积的影响。使用固定效应逻辑回归模型研究CTV覆盖情况的影响。
回顾了10次计划扫描和109次CBCT。放疗期间膀胱体积为45 - 578立方厘米，计划时为73 - 664立方厘米。膀胱体积随等待时间增加（4立方厘米/分钟），在治疗过程中减小（平均4立方厘米/天），化疗后更大（约50立方厘米）。膀胱体积与计划时相差>130立方厘米会导致计划靶区（PTV）无法覆盖CTV。PTV覆盖CTV的概率每偏离计划体积1立方厘米降低1.9%，主要影响子宫。计划膀胱体积>300立方厘米在治疗期间无法重现。直肠前后径与体积相关。整个治疗过程中未呈现出规律模式。PTV覆盖CTV的概率每偏离计划前后径1毫米降低5.8%，主要影响宫颈。如果治疗期间直肠比计划时大，PTV无法覆盖CTV的风险更高。随着膀胱体积减小，直肠前后径增加。
我们的数据表明理想的计划膀胱体积为150 - 300立方厘米，化疗后等待时间较短，整个治疗过程中充分补水。计划时及整个治疗过程中使用泻药可能也有益处。即便采取了这些措施，在对妇科癌症实施先进放疗技术时定期成像仍至关重要。
