Clinical Study On Combined Mode Of Internal And External Doses Of Local Advanced Cervical Cancer

Objective:In local advanced cervical cancer,the total dose of radiation therapy is the result of internal and external irradiation.The distribution of internal and external doses affects the total dose of high-risk clinical target volume（HR-CTV）and the risk of organ compromise.This paper aims to investigate the dose-splitting combination mode of dose-optimized internal and external irradiation when different prescription doses are given.Methods:Forty patients with cervical cancer who underwent radical radiotherapy were enrolled in our hospital.The internal irradiation was treated with interstitial implantation.The patients were randomly divided into two groups according to the different doses of internal irradiation.The first group was given a single prescription for internal irradiation.The dose was 7Gy,the number of divisions was 4 times,once a week,the second group was given a single prescription dose of 6Gy for internal irradiation,the number of divisions was 5 times,once a week,and the external dose was given 45Gy/25times.The irradiation dose was 50.4Gy/28 times,and all doses were converted to 2Gy equivalents.Groups 1 and 2 were set to 3 subgroups respectively:subgroup 1:HR-CTVD90 dose was 85Gy,bladder D_2cc limit was 90Gy,and rectum and sigmoid D_2cc limit was 75Gy.Subgroup 2:HR-CTVD90 dose is90Gy,bladder D_2cc limit is 90Gy,rectum and sigmoid D_2cc limit is 75Gy.Subgroup 3:HR-CTVD90 dose is 90Gy,bladder D_2cccc limit is 80Gy,rectum and sigmoid D_2cc limit is 70Gy.The doses of HR-CTVD90 and D_2cccc endangered organs were expressed as x±s.The comparison between doses was performed by rank sum test,P<0.05 was considered statistically significant.Results:1.The results of group 1 showed that there was no significant difference between the external doses of 45Gy and 50.4Gy in subgroup 1 and subgroup 3after HR-CTVD90（P>0.05）,and 45Gy external dose was given in subgroup2.The obtained HR-CTVD90 dose was higher,and the difference was statistically significant（P=0.028）.The results of the second group showed that there was no significant difference in the HR-CTVD90 between the external irradiation dose of 45Gy and 50.4Gy and the internal irradiation in the three subgroups（P>0.05）.The results of both groups showed that the D_2cccc of the rectum,bladder and sigmoid colon after administration of 45Gy external dose was lower than the external dose of 50.4Gy.The difference was statistically significant（P<0.05）.Therefore,the external dose of 45Gy combined with internal irradiation is more conducive to protection.Endangers organs.2.There was no significant difference in D_2cc dose between HR-CTVD90,rectum,bladder and sigmoid colon in the three subgroups after the external dose of 45Gy was combined with the first group and the second group（P>0.05）3.In group 1,18 patients in subgroup 1 completed the plan with 45Gy and 50.4Gy external exposure dose combined with internal irradiation.In subgroup 2,12 patients and 10 patients completed the plan.Seven patients and six patients in subgroup 3 completed the plan.In group 2,17 and 16 patients in subgroup 1 completed the plan with 45Gy and 50.4Gy external exposure dose combined with internal irradiation,and 11 patients in subgroup 2completed the plan in the subgroup.while in subgroup 3,5 patients and 4patients completed the plan.In subgroup 3,for patients with large HR-CTV volume,the external radiation dose of 50.4Gy combined with internal radiation resulted higher HR-CTVD90 dose.Conclusion:Considering the possible risks of implant treatment and patient compliance,the 1.8Gy×25 times external dose splitting mode is more advantageous than the 7Gy×4 times internal dose splitting mode.