Takatsu Jun, Murakami Naoya, Okonogi Noriyuki, Inoue Tatsuya, Iijima Kotaro, Muramoto Yoichi, Kosugi Yasuo, Kawamoto Terufumi, Karino Tatsuki, Terao Yasuhisa, Shikama Naoto
Department of Radiation Oncology, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
Department of Radiology, Juntendo University Urayasu Hospital, 2-1-1 Tomioka Urayasu-shi, Chiba 279-0021, Japan.
J Radiat Res. 2025 May 23;66(3):296-305. doi: 10.1093/jrr/rraf025.
The recommended dwell time weight of the needle in intracavitary/interstitial hybrid brachytherapy (HBT) has been 10-20%. This study aimed to investigate the correlation between the weight constraint of the needle and normal organ doses in uterine cervical cancer HBT. This study included 30 cervical cancer patients who received HBT with tandem/ovoid applicators. In our clinical practice, treatment plans were generated without the constraint of the dwell time weight of the needle. The cases where this weight exceeded 20% were replanned. An inverse planning technique with locking downscaled needle dwell time was used to reproduce isodose lines of clinical plans. Replanning repeated with downscaling of the dwell time until the weight of the needle fell <20% (Needle-Lock plan). The Needle-Lock plans were rescaled to coincide with the high-risk clinical target volumes D90 of clinical plans. D2cc in normal organs and the overdose area >200% of the prescribed dose were evaluated. In 17 of 30 (56.7%) clinical plans, the weight of the needle exceeded 20%. The rectum, bladder and sigmoid colon D2cc significantly increased with the Needle-Lock plan. The overdosage area also increased significantly (P < 0.01). The correlations between the needle number and the increase of D2cc in the rectum and sigmoid colon (P < 0.01) were statistically significant. Limiting needle dwell time weight by 10-20% increased bladder and rectum doses, especially with multiple needles. These findings suggest that needle dwell time weight recommendations could need to be reconsidered based on individual and institutional situation.
腔内/组织间混合近距离放射治疗（HBT）中推荐的针驻留时间权重为10%-20%。本研究旨在探讨子宫颈癌HBT中针的权重限制与正常器官剂量之间的相关性。本研究纳入了30例接受串联/卵圆形容器HBT的宫颈癌患者。在我们的临床实践中，治疗计划的生成未受针驻留时间权重的限制。当该权重超过20%时，重新制定计划。采用锁定缩小针驻留时间的逆向计划技术来重现临床计划的等剂量线。随着驻留时间的缩小重复重新计划，直到针的权重降至<20%（针锁定计划）。将针锁定计划重新缩放，使其与临床计划的高危临床靶体积D90一致。评估正常器官中的D2cc以及超过处方剂量200%的过量照射区域。在30例临床计划中的17例（56.7%）中，针的权重超过了20%。针锁定计划使直肠、膀胱和乙状结肠的D2cc显著增加。过量照射区域也显著增加（P < 0.01）。针的数量与直肠和乙状结肠D2cc增加之间的相关性具有统计学意义（P < 0.01）。将针驻留时间权重限制在10%-20%会增加膀胱和直肠的剂量，尤其是在针数较多的情况下。这些发现表明，可能需要根据个体和机构情况重新考虑针驻留时间权重的建议。
