宫颈癌卵巢移位术后IMRT与VMAT放疗对卵巢功能保护的剂量学评估

Dosimetric evaluation of ovarian function preservation using IMRT and VMAT radiotherapy following ovarian transposition surgery in cervical cancer patients

摘要:

目的 评估宫颈癌患者在接受卵巢移位术后，固定野调强放疗（IMRT）与容积旋转调强放疗（VMAT）在保护卵巢功能方面的剂量学优势。方法 选取2016年1月—2022年1月淮安市第二人民医院收治的44例宫颈鳞癌卵巢移位术后需行辅助放疗的患者。根据放疗方式不同分为IMRT组和VMAT组，每组22例。IMRT组采用9野均分共面照射，VMAT组采用双全弧共面照射。比较2种放疗方式的剂量学差异及对卵巢功能的影响，分析移位卵巢位置与卵巢剂量之间的关系。结果 IMRT在保留双侧卵巢时计划靶体积（PTV）的D_2%、D_98%、CI、HI各项参数均优于VMAT计划。在保护卵巢方面，IMRT卵巢D_mean（5.01±1.14）Gy、D_max（8.08±2.65）、V5（50.63±30.23）、V7（16.11±22.68）均低于VMAT计划（P <0.05）。对危及器官的保护，IMRT组患者治疗前后雌二醇的差值高于VMAT组患者（P <0.05），LH和FSH的差值均低于VMAT组患者（P <0.05）；两组治疗前后左右股骨头D_mean和直肠D_2%的差值比较，差异均无统计学意义（P >0.05）。单因素分析发现，IMRT治疗组与VMAT治疗组卵巢中心层面距同侧PTV的横向距离与卵巢平均剂量比较，差异均有统计学意义（P <0.05），IMRT治疗组卵巢平均剂量与卵巢中心层面距髂嵴平面纵向距离呈正相关（r =0.667，P <0.05），与卵巢中心层面距PTV最近距离、卵巢中心层面距同侧PTV横向距离均呈负相关（r = -0.824和-0.907，均P <0.05），同时与卵巢体积呈负相关（r = -0.370，P <0.05）。VMAT治疗组卵巢平均剂量与卵巢中心层面距髂嵴平面纵向距离呈正相关（r = 0.624，P <0.05），与卵巢中心层面距PTV最近距离、卵巢中心层面距同侧PTV横向距离均呈负相关（r = -0.804和-0.885，均P <0.05），同时与卵巢体积呈负相关（r = -0.340，P <0.05）。结论 通过剂量学比较，IMRT放疗在宫颈癌卵巢移位术后保护卵巢功能方面更具优势。通过测量卵巢中心层面距同侧PTV的横向距离可以预测卵巢剂量。

Abstract:

Objective To evaluate the dosimetric advantages of intensity-modulated radiation therapy (IMRT) versus volumetric-modulated arc therapy (VMAT) in preserving ovarian function in cervical cancer patients post-oophoropexy.Methods From January 2016 to January 2022, 44 patients with cervical squamous cell carcinoma who underwent oophoropexy and required adjuvant radiotherapy were selected from Huai'an Second People's Hospital. Patients were divided into IMRT and VMAT groups, with 22 cases in each group. The IMRT group received 9-field coplanar irradiation, while the VMAT group received dual-arc coplanar irradiation. The dosimetric differences and impact on ovarian function between the two radiotherapy modalities were compared, and the relationship between the location of the relocated ovaries and ovarian dose was analyzed.Results IMRT showed superior parameters for the planning target volume (PTV) including D_2%, D9_8%, conformity index (CI), and homogeneity index (HI) compared to VMAT. In terms of ovarian protection, IMRT had lower mean ovarian dose (D_mean 5.21 ± 1.34 Gy), maximum ovarian dose (D_max 8.28 ± 2.65 Gy), V5 (50.63 ± 30.23), and V7 (16.11 ± 22.68) compared to VMAT (P < 0.05). For organ at risk (OAR) protection, the change in estradiol (E₂) levels pre- and post-treatment was higher in the IMRT group than in the VMAT group (P < 0.05), while the changes in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were lower in the IMRT group (P < 0.05). No significant differences were observed in the changes in D_mean of the femoral heads and D_2% of the rectum between the two groups (P > 0.05). Univariate analysis revealed significant differences in the lateral distance from the ovarian central plane to the ipsilateral PTV between the IMRT and VMAT groups (P < 0.05). In the IMRT group, the mean ovarian dose was positively correlated with the vertical distance from the ovarian central plane to the iliac crest (r = 0.667, P < 0.05) and negatively correlated with the minimum distance to the PTV and lateral distance to the ipsilateral PTV (r = -0.824 and -0.907, respectively, both P < 0.05), as well as ovarian volume (r = -0.370, P < 0.05). In the VMAT group, the mean ovarian dose was positively correlated with the vertical distance from the ovarian central plane to the iliac crest (r = 0.624, P < 0.05) and negatively correlated with the minimum distance to the PTV and lateral distance to the ipsilateral PTV (r = -0.804 and -0.885, respectively, both P < 0.05), as well as ovarian volume (r = -0.340, P < 0.05).Conclusion Dosimetric comparison indicates that IMRT provides better protection for ovarian function in cervical cancer patients post-oophoropexy. The lateral distance from the ovarian central plane to the ipsilateral PTV can predict the ovarian dose.