The Clinical Resersarch Of Adaptive Intensity-Modulated Radiotherapy In Preoperative Cervical Cancer

Purpose:To validate the advantage of adaptive intensity-modulated radiotherapy among the preoperative patient of cervical cancer, the differences of volume, motion, dosimetry in the target area and organ at risk among the preoperative patient of cervical cancer who carried on adaptive radiotherapy were compared, also the curative effect and toxic side effects were evaluated.Materials and methods:21patients of preoperative cervical cancer with stage ⅠB2-ⅢB (FIGO2009stage) who decided to carry on the chemo-radiotherapy treatment were enrolled in this study. Weekly CT scans were obtained from these patients, target and organs at risk were outlined in the MIM Maestro software, then the ordinary IMRT plans and subsequent adaptive radiotherapy plan would be formulated, the total dose of planning gross tumor volume is53Gy,2.12Gy/fraction/day,5 days/week, the total dose of planning clinical tumor volume is45Gy,1.8Gy/fraction/day,5days/week. Delineated the OARs according to RTOG pelvic organs outline guide, the dose limited according to QUANTEC. The volume and the motion of target/organ at risk were collected by the CT sets.The setup errors were collected and analysed with bony registration and gray level registration mode, then calculating the external boundary.The initial CT scans were deformated to the new CT scans by MIM, and then calculates the actual dose on the new CT scans from the initial radiotherapy plan, the new plan plus the actual dose to build the cumulative dose. The initial DVHs were compared with DVHs after adaptive replanning through variance analysis of randomized block design.The recent curative effect of adaptive radiation and side effects were assessed according to RECSIT standard and RTOG acute radiation injury.Results:1. the average tumor volume was reduced to37.09%after the treatment.The most significantly shrinkage occurred during the second week (p=0.003), while the mode of shrinkage varied among the patients.There’s no correlation between the maximum diameter of the tumor, the initial tumor volume, the level of hemoglobin,stage and the average changes of tumor volume. Average of initial bladder volume was (270.93±129.44) cc, average of initial rectum volume was39.3cc (14.42-97.7cc),average of initial bowel bag volume was948.12cc (473.21-1615.38cc).The absolute value of varieable volume of bladder,rectum, bowel bag were (88.15±74.26) cc、9.12cc (4.12-17.16cc)、101.40cc (35.84-131.32cc) respectly.There’s no significant differences between the volume of organ at risk among the initial and weekly CTsets.2. Displacement of the mass of cervical at the direction of left-right, superior-inferior and anterior-posterior were (1.8±0.6) mm,(3.1±1.9) mm and (4.9±2.3) mm respectively. Displacement of the mass of bladder at the direction of left-right,superior-inferior and anterior-posterior were (2.6±1.8) mm.(19.5±8.3)mm、(9.1±3.4)mm respectively. Displacement of the mass of rectum at the direction of left-right,superior-inferior and anterior-posterior were (3.2±1.5) mm、(6.0±3.3)mm、(9.4±5.8)mm respectively. No statistical significance was found when the correlation analysis between cervical mass displacement and the changes of bladder, rectal volume. The displacement of cervical anterior wall were found correlation with the displacement of bladder posterior wall (r=0.282), the same to the displacement of cervical posterior wall and the displacement of rectal anterior wall (r=0.481).3.The average setup errors of patients with bony registration mode on the left-right,superior-inferior and anterior-posterior were (0.02±0.248) cm,(0.11±0.989) cm and (-0.06±0.32) cm respectively. As for the gray registration mode the results were (0.11±0.70) cm,(0.14±0.814) cm,(0.02±0.41) cm. No statistical significance was found between the same direction with different registration patterns (p=0.616, p=0.873, p=0.691). CTV-PTV margin were calculated according to the Van herk boundary formula with bone registration mode, the results were:2.24mm on left-right direction,9.67mm on superior-infierior direction and3.74mm on anterior-posterior direction. While it changed to1.55mm on lateral direction,9.20mm on superior-infierior direction and3.37mm on anterior-posterior direction with gray level registration mode.4. V53, V58.3, V49.29, D50, CI of PGTV and V45, CI of PCTV would decrease if we do not modify the plan, the V53, D50, CI of PGTV and V45, CI of PCTVwould improve when we revised the plan.5. As for organ at risk, if we do not modify the plan, V40and V50of bladder, V40and V50of rectum, V40, V45absolute volume, mean dose of bowel bag would increased, these indexes would decreased when we modified the plan except V40of rectum and mean dose of bowel bag. V50、V30and mean dose of the femoral head, V10, V20and mean dose of bone marrow were not found dosimetry different between initial plan and the modified plan.6. Evaluation of side effects and curative effect:the incidence of grade1-2gastrointestinal toxicity during the treatment was about61.9%, the data changed to4.7%when it turned to3-4gastrointestinal toxicity. The incidence of grade1-2hematological toxicity,3-4hematological toxicity was about52.4%and23.8%respectly. About61.9%of patients achieve PR according to image.14patients underwent operation. CR rate of postoperative pathology was42.85%, there’s no correlation between pathological CR and image PR, the initial tumor volume, the maximum diameter of tumor, hemoglobin level.Conclusion:1. Tumor regression is relatively significant at the second week but varies individually; the regression has no relationship with the initial tumor volume and maximum diameter of tumor.2. Bladder and rectal volume still varieties during radiotherapy even if given some preparation, correlation were found between displacement of bladder posterior wall and displacement of cervical anterior wall, correlation were also found between displacement of rectum anterior wall and displacement of cervical posterior wall.3. No statistical significance was found between the same directions with different registration pattern. CTV-PTV margin were2.24mm,9.67mm,3.74mm on left-right, superior-infierior and anterior-posterior direction with bone registration mode. When it turned to gray level registration mode, the result would be1.55mm,9.20mm,3.37mm on lateral, superior-infierior and anterior-posterior direction.4. Adaptive intensity-modulated radiotherapy can improve the coverage rate and comfort index of target area. 5. Adaptive intensity-modulated radiotherapy can reduce the dose level of rectum, bladder and bowel bags in certain dose level.6. Adaptive intensity-modulated radiotherapy showed a clear short-term effect and moderately side effects among the preoperative cervical cancer patients.