Hybrid Tomo-Helical and Tomo-Direct radiotherapy for localized prostate cancer

Comparative Evaluation of Dosimetric Quality and Treatment Efficiency for Halcyon, TrueBeam, and TomoTherapy in Cervical-Thoracic Esophageal Cancer Radiotherapy

INTRODUCTION

This study primarily aims to investigate the suitability of Halcyon in the context of cervical-thoracic esophageal cancer by exploring the dosimetric quality and delivery efficiency of Halcyon plans with different arc configurations. Additionally, it compares these findings with the dosimetric indices and delivery efficiency of TrueBeam and TomoTherapy accelerators, focusing on their capability to optimize protection for organs at risk (OARs) while maintaining efficient treatment delivery strategies.

METHODS

This retrospective study involved 26 patients diagnosed with cervical-thoracic esophageal cancer, and new radiotherapy plans were created using Halcyon, TrueBeam, and TomoTherapy. Dose volume histogram (DVH) metrics and delivery efficiency for plans involving different arc numbers on Halcyon (2, 3, and 4 arcs) were compared with those from TrueBeam and TomoTherapy. T-tests were employed to evaluate differences in organ protection among the accelerators.

RESULTS

The Halcyon plans, especially those with 4 arcs, provided superior protection for organs at risk, including the heart, lungs, and spinal cord, while maintaining excellent delivery efficiency. Compared to TrueBeam 2arc plans and TomoTherapy helical plans, Halcyon plans with 3 arcs also showed slight advantages. Although TomoTherapy offered better uniformity in dose distribution, it did not demonstrate a clear advantage over the other accelerators in terms of OAR protection or treatment efficiency. Furthermore, despite the lack of clear advantages in TrueBeam 2arc plans with flattening filter (FF), TrueBeam with flattening filter free (FFF) plans may hold potential in the treatment.

CONCLUSION

Halcyon, particularly with 4 arcs, offers an optimal balance between reducing toxicity to organs at risk and maintaining treatment efficiency, making it a preferred choice in cervical thoracic esophageal cancer radiotherapy. The findings highlight the need for careful selection of radiotherapy accelerators based on specific clinical goals, with Halcyon showing potential advantages in scenarios where both treatment efficiency and OAR protection are paramount.

Dosimetry comparison with helical tomotherapy, volumetric modulated arc therapy, and intensity-modulated radiotherapy for grade II gliomas: A single‑institution case series

Radiotherapy is an essential postoperative treatment for grade II gliomas. However, comparative dosimetric studies of different radiotherapy plans for grade II gliomas are still lacking. Therefore, we conducted this case series analysis to compare the dosimetric differences among helical tomotherapy (TOMO), volumetric modulated arc therapy (VMAT), and intensity-modulated radiotherapy (IMRT) for grade II gliomas. To achieve that, seven diagnosed postoperative patients with grade II gliomas were analyzed by computed tomography and then planned with TOMO, VMAT, and IMRT. The plan target volume (PTV) prescribed dose was 50 Gy (daily fraction of 2.0 Gy, 5 days/week). The expected treatment efficiency was measured by monitor units (MUs) scoring. Treatment plans of the patients were compared in the quality of target volumes dosage coverage, the efficiency of dosage delivery, and the dosage exposure of normal adjacent organs at risk (OAR). Differences in each method were measured by utilizing the Nonparametric ANOVA. The study shows that TOMO achieved a significantly higher PTV-D_98% (doses received by 98% of the PTV volume) than VMAT and IMRT (50.30 ± 0.13 vs 49.21 ± 0.19, p = 0.006; 50.30 ± 0.13 vs 49.78 ± 0.18, p = 0.014), while there was no difference in PTV-D_2% (doses received by 2% of the PTV volume). IMRT achieved a conformity index (CI) preferably, and TOMO generated a favorable homogeneity index (HI) (p < 0.05 for both). The MUs were fewer for VMAT than IMRT and TOMO (294 ± 19, 572 ± 24, 317 ± 97, respectively). IMRT achieved better protection for the lens and brain stems. Our case series study indicated that TOMO, VMAT, and IMRT achieved a comparatively good target dosimetric coverage, and most OARs were protected well. IMRT is not inferior to TOMO and VMAT and is still very suitable for treating most grade II glioma patients.

Hybrid Tomo-Helical and Tomo-Direct radiotherapy for localized prostate cancer

PURPOSE

The aim of the study is to present a new planning approach to provide better planning target volume (PTV) coverage and reduce bladder and rectum dose with hybrid Tomo-Helical (TH)/Tomo-Direct (TD) radiotherapy (RT) for localized prostate cancer (LPC).

METHODS

Twenty-five LPC patients were included in this retrospective study. TH plans, TD plans, and hybrid TH/TD plans were created. Lateral beams were used for the hybrid TD plan and the prescribed dose was 70 Gy in 28 fractions (hybrid plans were combined 45 Gy/ 18 fxs for TH and 25 Gy/10 fxs for TD). Doses of PTV (D2%, D98%, D50%, homogeneity index (HI), conformity index (CI), coverage) and organs at risk (OARs) (V50%, V35%, V25%, V5%, and V95%) were analyzed. The Wilcoxon signed-rank test was used to analyze the difference in dosimetric parameters. p-Value < 0.05 was considered statistically significant.

RESULTS

TH plans showed better CI, and target coverage (p < 0.01) than TD and hybrid plans in all patient plan evaluations. However, TD plans D2%, D98%, and D50% doses were better than TH and hybrid plans. The HI values were similar between the three plans. Significant reductions in bladder and rectum V50%, V35%, and V25% doses (p < 0.001) were observed with hybrid plans compared to TH and TD. Penile bulb V95% and bowel V5% doses were better in the hybrid plans. Left and right femoral head V5% doses were higher in the hybrid plan compared to others (p < 0.001).

CONCLUSION

Concurrently hybrid TH/TD RT plan can be a good option to reduce the doses of the rectum and bladder in the RT of LPC.