Influence Of Postoperative Target Volumes Delineating On Rectum Of Patients With Cancer Of Cervix In Three Dimensional Conformal Radiation Therapy

Objective To find the optimal clinical target volume(CTV) through study different target volumes in three dimension conformal radiation therapy(3D-CRT) for patients with stageⅠb～Ⅱa cervical cancer received preventive postoperative radiotherapy.The patients with stageⅠb～Ⅱa cervical cancer should receive operation as the first choice.If the patients have risk factors of recurrence,such as positive lymph nodes,deep invasion, positive edge, capillary lymphatic space involvement,huge tumer,they should receive adjuvant preventive postoperative radiotherapy.In this study,three weeks after operation,all patients who had recovered received preventive postoperative radiotherapy.Radiotherapy can improve the local control rates of stageⅠb～Ⅱa cervical cancer patients,lead to radiation proctitis and rectal impairment,and make the quality of life down.At present,the efficacy of the treatments for radiation proctitis is limited,so it is critical to prevent this side effect.Reducing the rectal volume recived radiation as much as possible becomes the focus of this issue.Considering the intimate relationship between the sacral lymph nodes and the rectum,the regularity of lymphatic metastasis of cervical cancer,we proposed that we might not delineate the sacral lymph nodes of clinical target volume to reduce the doses to rectum,so to relieve even evade the currence of radiation proctitis.The implement of this presumption is based on that without the radiation to sacral lymph nodes,local control rates and survival rates show no obvious changes.That is to say,we should not sacrifice the survival rates for the quality of life.Since the constant improvements of radiotherapeutic techniques,the widespread application of equipments used for three dimensional conformal radiation therapy,the developments of techniques of imaging and computer,we are supplied with these material bases.This study intends to offer a reference for enacting this standard.At present,there is not any report about the delineation of target volume in patients with cervical cancer.But as thedevelopment of the Evidence-based Medicine,the progress in clinical standardization and the medical technique,standardization of the radiotherapeutic taget vlume must be done in the near future.Methods From June of 2004 to April of 2006,46 patients with stageⅠb～Ⅱa cervical cancer received postoperative radiotherapy in our ward about three weeks after they were treated with radical operations.They were all confirmed by pathology and they have indication.With their information and consent,they were divided into the experimental group and the control group in random.The patients took oral contrast agent for better presentation of retume.We used enhanced scanning for the better delineation of target volume.At the same time,the patients kept holding urine in order to reduce radiation volume of bladder.The patients lied on the back,put their hands on their chests.The range of the scanning by CT simulation was from the inferior border of the third lumbar vertebra to the level of anus.The thickness of the scanning was five millimetrums.The data of image was transferred to the treatment planning system through network system,then they were rebuilt to form three dimensional images by computer.The delineation of the target volume was the critical link.There were many different taget volumes as the clinical experience,the knowledge and comprehension of different doctors were varied.In order to reduce the personal error as much as possible,this study requested the same doctor who masters radiotherapy and the other doctor who masters the imageology together to delineate the clinical target volume and OAR.The clinical target volume in the control group includes parauterine lymph nodes,uterine paracervical or paraureter lymph nodes,common iliac lymph nodes,internal and external iliac lymph nodes,obturator lymph nodes and sacral lymph nodes,while the clinical observational group's clinical taget volume did not include sacral lymph nodes.According to the determination of respiratory motion,cystic engorge,positioning error and concrete status,PTV was 7mm～10mm outer thanCTV.After the delineation of the target volume,physical specialist designed several reasonable treatment plans.These plans'eighty percentage to ninety percentage of isodose curve surround PTV.This isodose curve was considered as prescribed contour.The doctor who masters radiotherapy chose a better treatment plan to apply through comparison.Under the directions of the doctor who masters radiotherapy,the technician was in charge of appling the treatment plan.The patients recived radiation five times per week,two Gy per radiation,until the doses were accumulated to 46Gy～50Gy,then we added 4Gy～6Gy/2～3fractions to the cervical stump.The doctor who masters radiotherapy was in charge of handling the complication during the radiotherapy and directing the whole treatment.After the treatment,we collected statistics about the local control rate and currence of radiation proctitis through follow-up.Results We obtained the local control rate through follow-up.We used the CadPlan treatment planning system software to obtain the doses of 5% and 95% volume of rectum,maximum doses,minimum doses and mean doses.We used two independent sample t test.The local control rates of the two groups do not show an obvious difference,the doses of 5% and 95% volume of rectum(V5,V95) and the minimum doses,mean doses show obvious differences( tv5=2.169,pv5=0.041; tv95=4.036,pv95=0.001; tmean=2.236,pmean=0.036; tmin=2.265,pmin=0.034),the maximum doses of rectum showed no obvious difference(tmax=0.518,pmax=0.610),the currence of radiation proctitis showed obvious difference(p=0.004).Conclusions The differences of the doses of 5% and 95% volume of rectum(V5,V95),the minimum doses,mean doses between control group and clinical observational group led to the different currence of radiation proctitis.But the maximum doses of rectum showed no obvious difference.The reason may be that anterior wall of rectum close to cervical stump is the place absorbing maximum doses.The cervical stump was the common taget volumes in the two groups,so the maximum doses of rectumshowed no obvious difference.To sum up,the patients with stageⅠb～Ⅱa cervical cancer who have the risk factors of recurrence received 3D-CRT after radical operations.Through this prospective study,it is sure that their clinical target volume(CTV) delineations do not include sacral lymph nodes to avoid currence of radiation proctitis while they have content local control rates.There are 16 cases in the control group and 19 cases in the clinical observational group showed the zero grade or the first grade radiation proctitis.The effectiveness of clyster and nutrition was significant.The treatment improved the quality of life during our observation.Only one case in each group relapsed locally.Howerer the local control rates was considerly good.Thus,it is more important to improve the quality of life for the patients.