Objective To investigate the effects of titanium clip implantation under endoscope on target delineation and dosimetric parameters in patients with locally advanced esophageal cancer treated with preoperative radiotherapy.

Methods The clinical data of 36 patients with locally advanced esophageal squamous cell carcinoma confirmed by ultrasound gastroscopy and histopathology in the Joint Logistics Support Force Hospital 900 from January 2018 to December 2019 were retrospectively analyzed, including 23 males and 13 females, aged 18−65(43.7±6.9) years. All patients were treated with titanium clip implantation at the upper and lower boundaries of esophageal lesions under endoscopy before and after radiotherapy. CT scan localization and target delineation were performed before and after titanium clip implantation. Gross tumor volume (GTV) length, GTV, clinical target volume (CTV), and normal organ irradiation dose were compared before and after titanium clip implantation. The patients were divided into accurate group (error < 1 cm) and error group (error≥1 cm) according to the error value, and the influencing factors of esophageal target delineation were analyzed. Paired sample t-test and independent sample t-test were used to compare the error values of tumor length, diameter, upper bound and lower bound before and after titanium clip implantation, spinal cord, and heart as well as the difference of the average irradiation dose of double lung V₁₀ and V₂₀. χ² test was used to analyze the clinical case characteristics of the accurate group and the error group by univariate logistic regression. Cox multivariate regression risk factor analysis was used to analyze the risk factors affecting the accurate delineation of the target area.

Results Titanium clips were successfully placed under endoscope in all patients, but 4 cases (11.1%) had the upper boundary titanium clips falling off. The postoperative pathological complete response rate was 52.8% (19/36). The length of GTV before titanium clip implantation was (4.74±1.02) cm, which was higher than that after implantation (3.98±0.79) cm, and the difference was statistically significant (t=9.472, P<0.05). The GTV and CTV of the tumor before implantation were (28.87±3.21) cm³ and (72.46±6.37) cm³, respectively, which were higher than (24.59±2.67) cm³ and (56.37±4.52) cm³ after implantation. The differences were statistically significant (t=6.726, 7.696; both P<0.05). The irradiation doses of V₁₀, V₂₀ (the percentage of lung volume in total lung volume that received more than 10 Gy and 20 Gy irradiation dose, respectively), and spinal cord in both lungs before titanium clip implantation were higher than those after implantation ((21.64±1.57)% vs. (17.32±0.96)%, (14.87±2.32)% vs. (11.69±1.84)%, (28.87±3.21) Gy vs. (24.59±2.67) Gy), and the differences were statistically significant (t=8.05, 7.64, −2.43; all P<0.01). Univariate Logistic regression analysis showed that age, tumor location, drinking history, and GTV length were correlated with the accurate delineation of GTV (χ²=5.64, 11.57, 13.33, 8.23; all P<0.01). Cox multivariate regression analysis showed that tumor location and GTV length were independent risk factors affecting the accurate delineation of GTV (RR=0.296, 95%CI: 0.137~0.586; 2.313, 95%CI: 1.280~4.875; both P<0.01).

Conclusions Endoscopic titanium clip implantation is of great value in preoperative radiotherapy for locally advanced esophageal cancer. It can accurately guide the delineation of the target area under CT localization and reduce the irradiation dose of normal organs.