Alexander S E, Oelfke U, Westley R, McNair H A, Tree A C
The Royal Marsden NHS Foundation Trust, United Kingdom and The Institute of Cancer Research, United Kingdom.
The Joint Department of Physics, the Royal Marsden Hospital and the Institute of Cancer Research, United Kingdom.
Clin Transl Radiat Oncol. 2023 Sep 26;43:100685. doi: 10.1016/j.ctro.2023.100685. eCollection 2023 Nov.
Distended rectums on pre-radiotherapy scans are historically associated with poorer outcomes in patients treated with two-dimensional IGRT. Subsequently, strict rectal tolerances and preparation regimes were implemented. Contemporary IGRT, daily online registration to the prostate, corrects interfraction motion but intrafraction motion remains. We re-examine the need for rectal management strategies when using contemporary IGRT by quantifying rectal volume and its effect on intrafraction motion.
Pre and during radiotherapy rectal volumes and intrafraction motion were retrospectively calculated for 20 patients treated in 5-fractions and 20 treated in 20-fractions. Small (rectal volume at planning-CT ≤ median), and large (volume > median) subgroups were formed, and rectal volume between timepoints and subgroups compared. Rectal volume and intrafraction motion correlation was examined using Spearman's rho. Intrafraction motion difference between small and large subgroups and between fractions with rectal volume < or ≥ 90 cm were assessed.
Median rectal volume was 74 cm, 64 cm and 65 cm on diagnostic-MRI, planning-CT and treatment imaging respectively (ns). No significant correlation was found between patient's rectal volume at planning-CT and median intrafraction motion, nor treatment rectal volume and intrafraction motion for individual fractions. No significant difference in intrafraction motion between small and large subgroups presented and for fractions where rectal volume breached 90 cm, motion during that fraction was not significantly greater.
Larger rectal volumes before radiotherapy and during treatment did not cause greater intrafraction motion. Findings support the relaxation of strict rectal diameter tolerances and do not support the need for rectal preparation when delivering contemporary IGRT to the prostate.
在二维图像引导放射治疗（IGRT）中，放疗前扫描显示直肠扩张在历史上与患者较差的治疗结果相关。随后，实施了严格的直肠耐受性和准备方案。当代IGRT，即每日在线对前列腺进行配准，可校正分次间运动，但分次内运动仍然存在。我们通过量化直肠体积及其对分次内运动的影响，重新审视在使用当代IGRT时直肠管理策略的必要性。
回顾性计算了20例接受5次分割治疗和20例接受20次分割治疗患者放疗前及放疗期间的直肠体积和分次内运动。形成了小体积组（计划CT时直肠体积≤中位数）和大体积组（体积>中位数），并比较了时间点之间和亚组之间的直肠体积。使用Spearman等级相关系数检验直肠体积与分次内运动的相关性。评估了小体积组和大体积组之间以及直肠体积<或≥90 cm3的分次之间的分次内运动差异。
在诊断性MRI、计划CT和治疗成像时，直肠体积中位数分别为74 cm3、64 cm3和65 cm3（无显著性差异）。在计划CT时患者的直肠体积与中位数分次内运动之间，以及各分次的治疗直肠体积与分次内运动之间，均未发现显著相关性。小体积组和大体积组之间的分次内运动无显著差异，对于直肠体积超过90 cm3的分次，该分次期间的运动也没有显著更大。
放疗前和治疗期间较大的直肠体积不会导致更大的分次内运动。研究结果支持放宽严格的直肠直径耐受性，且不支持在对前列腺进行当代IGRT时进行直肠准备的必要性。
