A dosimetric study on TOMODirect treating locally advanced hypopharyngeal cancer

Abstract:

Objective：To analyze the dosimetric characteristics of TOMODirect（TD） on the treatment of locally advanced hypopha－ryngeal cancer and its tumor control probability（TCP），and to evaluate its clinical feasibility. Methods：Twenty-six patients with local－ly advanced hypopharyngeal cancer were randomly selected. TOMOHelical（TH） and TD were used to design radiotherapy plan. The paired t test was used in two different plans to analyze target envelope quality，organs at risk（OAR） protection，plan process and TCP. Results：All indexes of TD and TH treatment plans met clinical requirements. Compared with TH，the conformal index of PTV1 in TD plan was slightly worse（P=0.009），and the average dose was increased by 0.48%（P=0.010）. Dose differences of SIB and PTV2 in TH and TD plans were not significant，and has no statistical significance（P>0.05）. Compared with TH plan，only the maximum dose of spinal cord in TD plan was increased by 3.64%（P=0.044），and V5 Gy and V10 Gy were decreased by 3.98%（P=0.002） and 3.46%（P=0.002），respectively，while doses of other OARs in two plans had no significant difference，without statistical significance（P>0.05）. The number of monitor unit in TD plan was decreased by 8.04%（P=0.000） when compared with TH plan，but the treatment time was increased by 54.08 seconds（P=0.000）. Mean values of TCP in TD and TH plan were 94.74% and 94.71%，respectively，without statistically significant difference（P >0.05）. Conclusion：TD can obtain the similar target envelope and organ at risk with TH，reducing the volume of the low-dose area. Although the treatment time is prolonged，the number of monitor unit is reduced，and the average TCP is similar. TD may be a preferred radiotherapy method for treating locally advanced hypopharyngeal cancer，which is worthy of clinical promotion and application.