Comprehensive Comparison of Progressive Optimization Algorithm Based Automatic Plan and Manually Planned Treatment Technique for Cervical-Thoracic Esophageal Cancers

Impact of ovary-sparing treatment planning on plan quality, treatment time and gamma passing rates in intensity-modulated radiotherapy for stage I/II cervical cancer

BACKGROUND

This study aimed to investigate the impact of ovary-sparing intensity-modulated radiotherapy (IMRT) on plan quality, treatment time, and gamma passing rates for stage I/II cervical cancer patients.

METHODS

Fifteen stage I/II cervical cancer patients were retrospectively enrolled, and a pair of clinically suitable IMRT plans were designed for each patient, with (Group A) and without (Group B) ovary-sparing. Plan factors affecting plan quality, treatment time, and gamma passing rates, including the number of segments, monitor units, percentage of small-area segments (field area < 20 cm2), and percentage of small-MU segments (MU < 10), were compared and statistically analyzed. Key plan quality indicators, including ovarian dose, target dose coverage (D98%, D95%, D50%, D2%), conformity index, and homogeneity index, were evaluated and statistically assessed. Treatment time and gamma passing rates collected by IBA MatriXX were also compared.

RESULTS

The median ovarian dose in Group A and Group B was 7.61 Gy (range 6.71-8.51 Gy) and 38.52 Gy (range 29.84-43.82 Gy), respectively. Except for monitor units, all other plan factors were significantly lower in Group A than in Group B (all P < .05). Correlation coefficients between plan factors, treatment time, and gamma passing rates that were statistically different were all negative. Both Groups of plans met the prescription requirement (D95% ≥ 45.00 Gy) for clinical treatment. D98% was smaller for Group A than for Group B (P < .05); D50% and D2% were larger for Group A than for Group B (P < .05, P < .05). Group A plans had worse conformity index and homogeneity index than Group B plans (P < .05, P < .05). Treatment time did not differ significantly (P > .05). Gamma passing rates in Group A were higher than in Group B with the criteria of 2%/3 mm (P < .05) and 3%/2 mm (P < .05).

CONCLUSION

Despite the slightly decreased quality of the treatment plans, the ovary-sparing IMRT plans exhibited several advantages including lower ovarian dose and plan complexity, improved gamma passing rates, and a negligible impact on treatment time.

Multi-isocenter VMAT craniospinal irradiation using feasibility dose-volume histogram-guided auto-planning technique

This study aims to propose a novel treatment planning methodology for multi-isocenter volumetric modulated arc therapy (VMAT) craniospinal irradiation (CSI) using the special feasibility dose-volume histogram (FDVH)-guided auto-planning (AP) technique. Three different multi-isocenter VMAT -CSI plans were created, including manually based plans (MUPs), conventional AP plans (CAPs) and FDVH-guided AP plans (FAPs). The CAPs and FAPs were specially designed by combining multi-isocenter VMAT and AP techniques in the Pinnacle treatment planning system. Specially, the personalized optimization parameters for FAPs were generated using the FDVH function implemented in PlanIQ software, which provides the ideal organs at risk (OARs) sparing for the specific anatomical geometry based on the valuable assumption of the dose fall-off. Compared to MUPs, CAPs and FAPs significantly reduced the dose for most of the OARs. FAPs achieved the best homogeneity index (0.092 ± 0.013) and conformity index (0.980 ± 0.011), while CAPs were slightly inferior to the FAPs but superior to the MUPs. As opposed to MUPs, FAPs delivered a lower dose to OARs, whereas the difference between FAPs and CAPs was not statistically significant except for the optic chiasm and inner ear_L. The two AP approaches had similar MUs, which were significantly lower than the MUPs. The planning time of FAPs (145.00 ± 10.25 min) was slightly lower than that of CAPs (149.83 ± 14.37 min) and was substantially lower than that of MUPs (157.92 ± 16.11 min) with P < 0.0167. Overall, introducing the multi-isocenter AP technique into VMAT-CSI yielded positive outcomes and may play an important role in clinical CSI planning in the future.

Dose-volume comparison of intensity modulated proton therapy and volumetric modulated arc therapy for cervical esophageal cancer

Proton therapy for cervical esophageal cancer has many issues to be considered, such as the physiological curvature of the spine and the large range change from the neck to the trunk. We clarified the dosimetric characteristics of intensity modulated proton therapy (IMPT) for cervical esophageal cancer by comparing with volumetric modulated arc therapy (VMAT). Ten patients with cervical esophageal cancer were retrospectively planned for VMAT, 2-field IMPT (2F-IMPT), and 3-field IMPT (3F-IMPT). All plans were optimized to reach clinically acceptable levels. For planning target volume (PTV) coverage, 95% of the PTV should be covered by 95% of the prescription dose, unless the spinal cord limit is violated. The organs at risk included the lung, spinal cord, larynx, skin, and whole body. The prescription dose was 60 Gy relative biological effectiveness (RBE) in 30 fractions to the PTV. We compared the results according to dose-volume metrics. Significant dose reductions were achieved at lung doses, especially at low dose volumes of 20 Gy RBE or less in IMPT plans compared with VMAT plans (p < 0.05). Although the spinal cord PRV was below the tolerance level, the results were also significantly higher in VMAT plans than in IMPT plans (p < 0.001). Spinal cord PRV D_mean was significantly higher in 3F-IMPT than in 2F-IMPT (p < 0.001). In addition, it was confirmed that the integral whole body dose can be dramatically reduced in IMPT plans compared with VMAT plans. Both of 2F-IMPT and 3F-IMPT could effectively reduce spinal cord dose, as well as low integral whole body dose to a certain extent, while maintaining similar target coverage compared to VMAT. IMPT could be a promising treatment technique for patients with cervical esophageal cancer.