Three-Dimensional Conformal And Intensity-Modulated Whole Pelvic Radiotherapy In Posthysterectomy Cervical Carcinoma

Part 1 Establishment of three-dimensional conformal and intensity-modulated whole pelvic radiotherapy in posthysterectomy cervical carcinomaPurpose To establish the methods and to evaluate influencing factors for delineating CTV and PTV for three-dimensional conformal (3DCRT) and intensity-modulated radiotherapy (IMRT) for whole pelvic irradiation in posthysterectomy cervical carcinoma.Materials and Methods During 2004～2005, patients with cervical carcinoma underwent hysterectomy with high-risk of recurrence were selected for this study. The following observations and measurements were used for study: (1) Set-up errors for 10 patients with supine or prone position were measured to choose appropriate immobile position. (2) To measure different status of bladder (full or empty) and influence on irradiated volume of bladder and small bowel. (3) Patients were immobilized by vacuum-lock before CT simulation. With three-dimensional treatment planning system (ADAC Pinnacle~3), CTV including regional pelvis lymph nodes and tumor bed was delineated for each patient. (4) To measure treatment errors detected by EPID (electronic portal imaging device) and delineation for PTV. SPSS 11.0 was used for statistic analysis.Results It is found that (1) With prone immobilization, the set-up error was within 5 mm at three dimensions, while it was more than 5 mm with supine position. There is significant difference between the two positions. (2) The percentage of irradiated volume of bladder and small bowel were smaller when bladder was full status compared with empty status if other factors were balanced. (3) Guideline of contouring CTV by delineating tumor bed and pelvic vessels with 1 cm margin was put forward with supine or prone position. (4) With prone position, full status of bladder, EPID showed movement of three direction of isocenter of treatment. The random error was 3.1 mm ± 1.2 mm, system error was 6.7 mm ±1.1 mm, totaluncertainty was 7.4 mm ± 1.6 mm. For 95% confidence interval, the margin added to CTV to become PTV could be 1 cm.Conclusions Prone position was better than supine position for immobilization due to small set-up error. The status of bladder should be controlled during radiotherapy and full status seemed better. Guideline of contouring CTV was established. PTV could be contoured by adding 1 cm margin to CTV.Part 2 Evaluation of 3DCRT and IMRT dosimetric studies in posthysterectomy cervical carcinomaPurpose To establish the treatment planning methods for 3DCRT and IMRT and to undergo three-dimensional dosimetric studies for optimization of treatment planning.Materials and Methods During 2004～2005, 10 patients with cervical carcinoma underwent hysterectomy with high-risk of recurrence were selected for this study. Patients were immobilized by vacuum-lock before initial X-ray simulation and CT simulation. AcQSim 4.9.2 CT simulator, Pinnacle~3 (?) V7.0 contouring working station and Pinnacle~3 (?) (RTP system 7.0g) treatment planning system were used for dosimetric studies, including (1) Three different margins were added to CTV to generate PTVA, PTVB and PTVC. PTVA consisted CTV with 1 cm margin at all direction. PTVB consisted CTV with 0.5 cm margin at lateral and posterior and 1 cm margin at other direction. The irradiated normal tissues volume was compared when different PTVs were used for treatment planning. (2) Optimization of IMRT planning consisted of tolerance dose of organs at risk; volume at PTV and CTV at reference dose level; conformity index (CI), monitor unit (Mu) and segments of fields. (3) Three-dimensional conformal radiotherapy consisted of 3 fields, 4 fields, 5 fields, and 6 fields planning, while IMRT consisted of 5 fields, 7 fields, 9 fields, 11 fields, and 13 fields planning. Dose-Volume Histogram (DVH) was used to evaluate conventional 2 fields planning vs. 3DCRT vs. IMRT planning. SPSS 11.0 was used for statisticanalysis.Results With the expansion of PTV from PTVB to PTVA and PTVC, the percentage of irradiated volume of normal tissues (intestine, bowel, rectum, bladder, and bone) was increased. CI (PTV) for 3F, 4F, 5F, and 6F 3DCRT was 0.46, 0.67, 0.68, and 0.68, respectively, and 4F, 5F, and 6F planning were better than 3F planning when comparing the irradiated volume of normal tissues. However, beyond 4F, the advantage of increasing fields was not significant. So, it was found that 4F planning is feasible for clinical use. CI (PTV) for 5F, 7F, 9F, 11F, and 13F IMRT was 0.75, 0.83, 0.84, 0.85, and 0.85, respectively, and 7F, 9F, 11F, and 13F planning were better than 5F planning when comparing the irradiated volume of normal tissues. However, beyond 9F, the advantage of increasing fields was not significant. So, it was found that 9F planning was feasible for clinical use. The advantage of IMRT at dosimetry was significant compared with conventional or 3DCRT by means of sparing normal tissues.Conclusions Three-dimensional dosimetric studies were used for posthysterectomy cervical carcinoma patients. In 3DCRT planning, 4F planning is better and feasible for clinical use. In IMRT planning, 9F planning is feasible for clinical use. Different margins added to CTV to generate PTV will influence the irradiated normal tissues. It was important to select appropriate PTV for different patients. IMRT had advantage at sparing normal tissues compared with conventional 2 fields techniques and 3DCRT.Part 3 Clinical applications of 3DCRT and IMRT in posthysterectomy cervical carcinomaPurpose Clinical applications of 3DCRT and IMRT in posthysterectomy cervical carcinoma were studied. The feasibility of 3DCRT and IMRT were evaluated by treatment outcome and acute toxicity.Materials and Methods During September 2004 to December 2005, 15 cases received IMRT while 5 cases received 3DCRT. Among them, 10 patients of cervicalcarcinoma after hysterectomy were treated by IMRT while the other 5 patients were treated with 3DCRT. 2 patients with recurrence disease after hysterectomy were treated with IMRT. 1 patient with recurrence disease after hysterectomy and conventional 2 fields whole pelvic radiation 2 years before were retreated with IMRT due to poor response to chemotherapy. 2 patients with positive para-aortic lymph nodes and pelvic lymph nodes after hysterectomy were treated with IMRT. Radiotherapy was given once a day, 5 times a week, with 1.8 Gy per fraction. The prescribed dose was 45 Gy at PTV for whole pelvic irradiation, and 60 Gy at CTV for recurrent patients. EPID films were taken twice a week comparing with DRR to ensure the quality. RTOG acute toxicity scoring criteria was used to evaluate the radiation morbidity including GI, GU and haematological system toxicity. Last follow-up time was March 2006. Follow-up rate was 100%. The median follow-up time was 7.9 months (range 3～16 months). SPSS 11.0 was used for statistic analysis.Results No local recurrence or distant metastasis were observed during the follow-up duration. Except 1 case, no RTOG grade 3 or higher toxicity was observed in GI and haematological system. No RTOG grade 3 or higher toxicity was observed in GU. For posthysterectomy patients and patients with recurrence after hysterectomy, minor radiation morbidity was observed when whole pelvic IMRT and 3DCRT were used. However, for patients underwent re-radiation after recurrence or radiation field including para-aortic and pelvic areas, the radiation toxicity was relatively higher.Conclusions The application of 3DCRT and IMRT in posthysterectomy cervical carcinoma was acceptable with minor radiation toxicity. We found that with experience, IMRT is feasible in a busy clinic. Our results suggest that the normal tissue sparing achieved by IMRT will translate into less acute toxicity. However, longer follow-up and more cases are needed for the development of this new technique. Other areas of radiation using IMRT and IMRT combined with other treatment (e.g. chemotherapy) will be the future concern.