Plan-Optimization Method for Central-shielding Pelvic Volumetric-modulated Arc Therapy for Cervical Cancer

Abstract

Aim: To establish a method of plan optimization in pelvic volumetric-modulated arc therapy (VMAT) for cervical cancer using the central-shielding (CS) principle. Patients and Methods: We created external beam VMAT plans for eight cases with non-bulky stage I-IIb using the CS principle based on the Japanese standard guideline. Clinical target volumes (CTVs) for whole-pelvis (WP) irradiation were created using published guidelines, and CTVs for CS irradiation were created by subtracting the uterus corpus and 4 cm-wide regions centered at the cervix and vagina from the CTVs for WP irradiation. For plan optimization of CS irradiation, a 4-cm diameter cylindrical volume centered in the cervix and vagina was created as the volume receiving a high dose in brachytherapy, and the volume overlapping with the rectum was defined as the Ant-Rectum. Dosevolume histogram (DVH) parameters of two CS VMAT plans with and without (VMAT OPT /VMAT NO ) dose optimization to the Ant-Rectum were compared. Results: VMAT OPT plans resulted in significantly lower DVH parameters of the Ant-Rectum and rectum compared to VMAT NO plans. These were comparable to the DVH parameters of three-dimensional conformal radiotherapy (3DCRT) plans. Both VMAT plans resulted in significantly better coverage of planning target volumes than did the 3DCRT plans. Conclusion: In the implementation of IMRT/VMAT as the standard treatment for cervical cancer in Japan, our optimization method may be an essential step toward fully benefitting from the CS principle.

Intensity-modulated radiation therapy with the central shielding technique for patients with uterine cervical cancer

“…PTV for WPRT was defined as the combination of the primary PTV, prophylactic nodal PTV and involved nodal PTV. For the treatment planning of CS-WPRT, a 3.5–4.0 cm wide CS block with the same thickness as the body was placed virtually at the center of the pelvis [ 12 ]. The cranial side of the CS block was positioned to avoid overlapping with prophylactic PTV.…”

Plan quality and treatment efficiency assurance of two VMAT optimization for cervical cancer radiotherapy

“…Currently, many studies have focused on minimizing the delivery time while ensuring the quality of radiotherapy planning. 15 , 16 , 17 , 18 With the introduction of UIH 506C linac and TPS, we investigated the four plans difference in the two optimization algorithm with different fixed jaw to provide a basis for the selection of clinical radiotherapy techniques.…”

Combined Interstitial and Intracavitary High-Dose Rate Brachytherapy of Cervical Cancer

“…In many Japanese institutions, central shielding is used routinely for IIIB patients after 30 Gy of the whole pelvis EBRT ( 19 ), therefore central shielding pelvic radiation therapy was employed as the EBRT in this study, and IMRT was not accepted. In Japan, currently, an increasing number of institutions are transitioning to IMRT from central shielding in order to increase the dose to the primary ( 20 ). HBT was administered with 6 Gy 4 times, twice weekly immediately after completion of the whole pelvic radiation therapy.…”