Gautam Suman, Flower Emily, Richeson Dylan, Sangha Ikchit, Ma Tianjun, Song William Y
Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA.
Sydney West Radiation Oncology Network, Westmead, New South Wales, Australia; Institute of Medical Physics, University of Sydney, Camperdown, New South Wales, Australia.
Brachytherapy. 2025 Jan-Feb;24(1):144-153. doi: 10.1016/j.brachy.2024.11.001. Epub 2024 Dec 6.
The bladder and rectal toxicities in cervical cancer brachytherapy are positively correlated with the DVH parameter: D2cc. This study evaluates the feasibility of knowledge-based planning to predict the D2cc, identify suboptimal plans, and improve the plan quality with Direction Modulated Brachytherapy (DMBT) applicators using knowledge-based planning based on linear relationship between overlap distances and D2cc.
The overlap volume histogram (OVH) method was used to determine the distances for 2 cm of overlap between the Organs at Risks (OAR) and High-Risk Clinical Target Volume (CTV). Linear plots were utilized to model the OAR D2cc and 2 cm overlap distances. Two datasets from 45 patients (125 plans) were used to create 2 independent models: Model 1 from 59 Intracavitary (IC) and Model 2 from 66 Intracavitary-Interstitial (ICIS) plans. Performances were compared using 5-fold cross-validation. The predicted D2cc values were used as the maximum constraints in the inverse planning optimization.
The mean bladder D2cc decreased by 4.3% and 10.3% for conventional applicators, and 4.4% and 3.6% for DMBT applicators for Models 1 and 2, respectively. The rectum D2cc decreased by 3.4% and 10.7% for conventional and 3.0% and 5.0% for DMBT applicators, respectively. The sigmoid D2cc decreased by 3.1% and 6.9% for conventional and 3.2% and 5.9% for DMBT applicators, respectively. There were also significant reductions for the recto-vaginal (RV-RP) point and posterior-inferior border of symphysis (PIBS) reference points: PIBS+2cm, PIBS+1cm, PIBS-1cm, and PIBS-2cm, for both models as well.
A knowledge-based planning method successfully predicted D2cc and optimized brachytherapy plans for cervical cancer. The proposed model demonstrates the feasibility of predicting D2cc, detecting suboptimal plans, and improving the plan quality especially for DMBT where cumulative clinical experience is limited.
宫颈癌近距离放射治疗中的膀胱和直肠毒性与剂量体积直方图（DVH）参数D2cc呈正相关。本研究评估基于知识的计划的可行性，以预测D2cc、识别次优计划，并使用基于重叠距离与D2cc之间线性关系的基于知识的计划，通过方向调制近距离放射治疗（DMBT）施源器提高计划质量。
使用重叠体积直方图（OVH）方法确定危及器官（OAR）与高危临床靶区（CTV）之间2 cm重叠的距离。利用线性图对OAR D2cc和2 cm重叠距离进行建模。来自45例患者（125个计划）的两个数据集用于创建2个独立模型：模型1来自59个腔内（IC）计划，模型2来自66个腔内-间质（ICIS）计划。使用5折交叉验证比较性能。预测的D2cc值用作逆向计划优化中的最大约束。
对于模型1和模型2，传统施源器的膀胱平均D2cc分别降低了4.3%和10.3%，DMBT施源器分别降低了4.4%和3.6%。直肠D2cc，传统施源器降低了3.4%和10.7%，DMBT施源器分别降低了3.0%和5.0%。乙状结肠D2cc，传统施源器降低了3.1%和6.9%，DMBT施源器分别降低了3.2%和5.9%。对于两个模型，直肠阴道（RV-RP）点和耻骨联合后下缘（PIBS）参考点（PIBS+2cm、PIBS+1cm、PIBS-1cm和PIBS-2cm）也有显著降低。
一种基于知识的计划方法成功地预测了D2cc并优化了宫颈癌近距离放射治疗计划。所提出的模型证明了预测D2cc、检测次优计划以及提高计划质量的可行性，特别是对于累积临床经验有限的DMBT。
