Dosimetric analysis of plans using x-ray and γ-ray combination strategy for advanced cervical cancer patients with...

Radiotherapy is a standard treatment for locally advanced cervical cancer. Based on the inherent characteristics of X-ray and γ-ray radiation techniques, we propose and investigate an innovative dual-modality radiation system incorporating both X-ray and γ-ray modalities. This study compares the quality of radiation treatment plans for patients with CC, generated using the dual-modality (TaiChi) system and a conventional LINAC X-ray system.

Retrospective treatment plans using volumetric modulated arc therapy were selected for 12 patients with CC. Dual-modality plans were developed for these patients. All patients had the same prescription dose of 50 Gy/25 fractions for planning tumor volume (PTV) and 60 Gy/25 fractions for PTV-nd. The dose conformity index (CI) and gradient index (GI) were calculated to evaluate the dose coverage and drop for the target. The dose indices, Dmean, Dmax, and Dmin, were calculated for both the target and organs at risk (OARs).

Both strategies generated dosimetrically acceptable plans. For both PTV-nd and PTV, the plans of TaiChi demonstrated higher CI values (PTV-nd: 0.68 ± 0.11 vs. 0.57 ± 0.22, P-value = 0.1375; PTV: 0.91 ± 0.02 vs. 0.90 ± 0.02, P-value = 0.1053) and lower GI values (PTV-nd: 280.62 ± 302.86 vs. 300.65 ± 317.83, P-value = 0.0094; PTV: 3.36 ± 0.22 vs. 3.66 ± 0.32, P-value = 0.0015) compared with the plans of the conventional LINAC system. For both PTV-nd and PTV, the TaiChi plans exhibited superior dosimetric indices compared to the LINAC plans. Specifically, the Dmax (78.27±5.20 Gy vs. 66.61±1.51 Gy) and Dmean (66.85±1.61 Gy vs. 63.22±1.03 Gy) of the TaiChi plans were significantly higher than those of the LINAC plans. Although the Dmin (61.06±0.52 Gy vs. 60.46±1.33 Gy) of the TaiChi plans was also higher than that of the LINAC plans, the difference was not statistically significant. Moreover, TaiChi plans significantly reduced radiation exposure to OARs compared to LINAC plans, demonstrating improved organ protection. This was particularly evident for the spinal cord PRV, with the TaiChi plans yielding a maximum dose of 23.61±2.80 Gy, compared to 29.85±3.23 Gy for the LINAC plans (P-value = 0.0005).

The dual-modality system has the potential to enhance treatment outcomes in CC by optimizing tumor coverage while reducing toxicity. Future clinical trials should assess its impact on patient survival and treatment-related side effects to bridge the gap between dosimetric improvements and clinical application.