Comprehensive Treatment Uncertainty Analysis and PTV Margin Estimation for Fiducial Tracking in Robotic Liver Stereotactic Body Radiation Therapy.

OBJECTIVE: This study aims to quantify the uncertainties of CyberKnife Synchrony fiducial tracking for liver stereotactic body radiation therapy (SBRT) cases, and evaluate the required planning target volume (PTV) margins. METHODS: A total of 11 liver tumor patients with a total of 57 fractions, who underwent SBRT with synchronous fiducial tracking, were enrolled for the present study. The correlation/prediction model error, geometric error, and beam targeting error were quantified to determine the patient-level and fraction-level individual composite treatment uncertainties. The composite uncertainties and multiple margin recipes were compared for scenarios with and without rotation correction during treatment. RESULTS: The correlation model error-related uncertainty was 4.3±1.8, 1.4±0.5 and 1.8±0.7 mm in the superior-inferior (SI), left-right, and anterior-posterior directions, respectively. These were the primary contributors among all uncertainty sources. The geometric error significantly increased for treatments without rotation correction. The fraction-level composite uncertainties had a long tail distribution. Furthermore, the generally used 5-mm isotropic margin covered all uncertainties in the left-right and anterior-posterior directions, and only 75% of uncertainties in the SI direction. In order to cover 90% of uncertainties in the SI direction, an 8-mm margin would be needed. For scenarios without rotation correction, additional safety margins should be added, especially in the superior-inferior and anterior-posterior directions. CONCLUSION: The present study revealed that the correlation model error contributes to most of the uncertainties in the results. Most patients/fractions can be covered by a 5-mm margin. Patients with large treatment uncertainties might need a patient-specific margin.

Current status of neoadjuvant therapy for locally advanced rectal cancer in Wuhan Union Hospital Cancer Center.

BACKGROUND: To analyze and explore the evolution and short-term efficacy of neoadjuvant therapy for patients with mid and low LARC in Wuhan Union Hospital Cancer Center. METHODS: Patients diagnosed with rectal cancer from January 2015 to December 2021 were collected. The treatment patterns, short-term efficacy and treatment-related adverse events (AEs) of mid and low LARC patients who received neoadjuvant therapy were analyzed. The Chi-square test was used to compare the differences between groups. RESULTS: A total of 980 patients with mid and low LARC were enrolled, over time, the proportion of patients receiving neoadjuvant therapy gradually increased, and the treatment mode of direct surgery after diagnosis was gradually watered down. More than 80% of the patients implemented radiotherapy-based neoadjuvant therapy, and the proportion of patients receiving SCRT sequential systemic therapy gradually exceeded that of LCRT combined chemotherapy after 2020. Of all patients who completed radiotherapy and underwent surgery, 170 patients received long-course chemoradiotherapy (LCRT) combined with chemotherapy (Group C) and 98 patients received short-course radiotherapy (SCRT) combined with systemic therapy (chemotherapy with or without immunotherapy) (Group D). The pathological complete response (pCR) rate in Group D was significantly higher than that in Group C (38.8% vs. 19.4%, P = 0.001). The pCR rate in the SCRT plus immunotherapy group was better than that in the group without immunotherapy (49.2% vs. 21.6%, P = 0.007). 82.3% of the patients receiving immunotherapy were treated with SCRT sequential 2-cycle CapOX plus Camrelizumab treatment, and the pCR was as high as 52.9%. Immunotherapy did not increase the incidence of Grade 3-4 AEs. CONCLUSIONS: Neoadjuvant therapy based on radiotherapy is becoming used in patients with mid and low LARC. SCRT sequential systemic therapy is increasingly widely used in LARC patients in our center. Compared with the traditional LCRT or SCRT sequential chemotherapy, SCRT sequential chemotherapy plus immunotherapy has a remarkable pCR rate and manageable toxicity. Looking forward this new treatment mode will bring lasting survival benefits to patients.