Z. Wang; Department of Radiation Oncology, Xijing Hospital, Fourth Military Medical University, Xian, Shaanxi, China
Purpose/Objective(s): A new radiotherapy platform integrating a linear accelerator (linac) and a non-invasive stereotactic radiosurgery instrument has been approved for clinical use (NMPA: 20223050973; FDA: K210921), providing a novel radiotherapy technique combining X-ray and ?-ray. The purpose of this study is to investigate the dosimetric advantages of this technique for the treatment of patients with cervical cancer. Materials/
Methods: In this retrospective study, volumetric-modulated arc therapy (VMAT) clinical linac treatment plans of 10 cervical cancer patients with lymph node metastasis were randomly selected for comparison with combined plans using the new technology. The prescribed dose to the planning target volume (PTV) and PTV with lymph nodes (PTVLn) were 50Gy/25F and 62.5Gy/25F, respectively. Clinical treatment plans were generated using the technology company 13.5 treatment planning system(TPS) based on technology company linac with 6MV, while the combined plans were generated using the RT PRO TPS based on the new radiotherapy platform. The combined plans involved optimizing a linac plan (6MV) to cover the PTV, followed by escalation of the PTVLn dose using a non-invasive stereotactic radiosurgery instrument, while maintaining clinically tolerable doses to organs at risk (OARs). Dosimetric comparisons between the clinical linac treatment plans and combined plans were conducted to evaluate the ability of the technique to increase the PTVLn dose while minimizing the doses to OARs. Results: All plans met clinical requirements. When compared with clinical linac treatment plans, the combined plans demonstrated a significantly higher mean dose (Dmean) of PTVLn (67.80 ± 1.13Gy vs. 62.56 ± 1.00Gy, p=0.009) and a similar Dmean of PTV (50.5 ± 7.56Gy vs. 50.87 ± 8.24Gy, p=0.06). Furthermore, the combined plans showed lower or similar doses to OARs: Bladder V45 (38.98 ±10.23Gy vs. 42.34±9.75Gy, p=0.024) and D2cc (55.69±3.25Gy vs. 55.74±3.43Gy, p=0.558); Rectum V45 (52.08±0.76Gy vs. 52.7±0.37Gy, p=0.034), D2cc (57.19 ± 3.99Gy vs. 57.39 ± 4.98Gy, p=0.551); Small intestine V45 (372.5 ± 96.7 cc vs. 376.1 ± 92.04 cc, p=0.079), D2cc (57.19 ± 3.99Gy vs. 57.39 ± 4.98Gy, p = 0.551); The left femoral head V30 (6.67±1.86% vs. 11.1± 0.73%, p=0.04), the right femoral head V30 (7.15 ± 1.75% vs. 10.3 ± 1.85%, p=0.096). Conclusion: Based on the physical properties of X-rays and ?-rays, the results suggest that this new radiation therapy technique is feasible for escalating the lymph node dose and reducing doses to OARs. The technique may hold potential benefits for cervical cancer patients with lymph node metastasis.
