Dosimetric And Clinical Study In Adjuvant Radiotherapy Of Cervical Cancer After Surgery

Objective:To research the application of Rapid Arc in cervical squamous cell carcinoma after surgery,compare the differences in target coverage,conformity and homogeneity between Rapid Arc and IMRT;and evaluate the protective effects of OARs through analyzing dosimetric parameters in rectum,bladder,pelvis and so on.Meanwhile,the recent side effects appeared in radiotherapy of cervical cancer of the two techniques were also assessed to provide reference for choosing clinical radiotherapy technique of cervical squamous cell carcinoma after surgery.Methods:Fifty-one patients pathologically diagnosed with cervical squamous cell carcinoma and accepted extensive hysterectomy+pelvic lymph node dissection were recruited.Make sure that all of them underwent simulated position and CT scan with an identical procedure,than delineate tumor targets and organs at risk according to international standard.All the plans were verified by one intermediate and one senior radiation oncologists.Patients were subdivided into the Rapid Arc or IMRT arms according to the techniques prescribed.We compared the dosimetric parameters of PTV,conformation index（CI）,homogeneity index（HI）to evaluate the target coverage,conformity and homogeneity.Comparing monitor units（MU）to evaluate the efficacy of the two techniques.While the dosimetric parameters of organs at risk were compared to estimate the protective ability between the two techniques;the occurrence of acute irradiation injuries were compared to assess the safety,effectiveness and feasibility of Rapid Arc.Results:1.Comparisons of general clinical information:There was no significant difference in demographic characteristics（ages,scores of ECOG and clinical stages）between two arms（P>0.05）.The accepted data of them can be compared.2.Comparisons of dosimetric parameters of PTV and monitor units（MU）:The MU of Rapid Arc（times）[（614.00±91.75）vs（1576.35±418.70）]was smaller than that of IMRT,the difference was statistically significant（p<0.05）;However,there was no significant difference in the CI and HI between the two arms（p>0.05）.Besides,there was also no significant difference in D₂、D₉₈、D₅₀of PTV（P>0.05）.3.Comparisons of dosimetric parameters of OARs:V₄₀of rectum was significantly higher in Rapid Arc than IMRT[（44.45±4.18）vs（40.54±5.22）]（P<0.05）.Meanwhile,V₂₀[（77.00±5.55）vs（82.78±4.36）]and V₃₀[（47.21±9.15）vs（52.43±6.86）]of pelvis in Rapid Arc were lower than those in the IMRT（p<0.05）.No other difference in organs at risk showed statistical significance（P>0.05）.4.Comparisons of acute radiation injuries:The incidence of acute radiodermatitis in Rapid Arc showed slightly lower than IMRT（p<0.05）,which incidence rate reduce by 32.10%.There was no significant difference in other acute radiation injuries between the two arms（P>0.05）.Conclusions:1.Rapid Arc could meet the dosimetric requirements of target coverage as well as IMRT.Two techniques can also provide comparatively superior target coverage,conformity and homogeneity.While Rapid Arc reduce monitor units remarkably.2.Rapid Arc performed better in reducing the radiation dosage of pelvis than IMRT which shows better protective ability for pelvis.3.Rapid Arc exhibited superiority in alleviating dermal,digestive and urinary toxicity,while difference in acute radiodermatitis was statistically significant.It was illustrated that Rapid Arc have advantage in reducing acute irradiation injuries.