Technical and dosimetric study of three-dimensional conformal and intensity-modulated pelvic radiotherapy for post-hysterectomy cervical carcinoma / 中华放射肿瘤学杂志

ABSTRACT

Objective To establish the methods of three-dimensional eonformal(3DCRT) and intensity-modulated radiotherapy(IMRT) for whole pelvic irradiation in post-hysterectomy cervical carcinoma, And to optimize the methods for clinical practice. Methods Between 2004 and 2005,10 patients with cervical carcinoma who underwent hysterectomy with high risk of recurrence were selected for this study. The following observations and measurements were used for the study Set-up errors with supine or prone position were measured to determine appropriate immobilization position. Influence of full and empty bladder on irradiated normal tissue volume was measured. Treatment errors were detected and CTV/PTV were then delineated. 3DCRT and IMRT planning and comparison were applied. Results The set-up error was within 5 mm of three dimensions in prone position and more than 5 mm in supine position, the difference of which was statistically significant. The percentage of irradiated volume of the bladder and bowel was smaller when the bladder was full comparing with empty bladder. In prone position and with full bladder,portal films showed the movement of isocenter in three directions. The total uncertainty was [7.4±1.6]mm. For 95% confidence interval,the margin from CTV to PTV was 1 cm. CIPTV for 3,4,5,and 6 fields 3DCRT was 0.46,O. 67, O. 68, and O. 68, respectively. When beyond 4 fields, the advantage of adding fields was not significant.Four fields planning was feasible for clinical practice. CI for 5,7,9,11 ,and 13 fidds IMRT was 0.75,0.83, 0.84,0.85 ,and 0.85 ,respectively. When beyond 9 fields,the advantage of adding fields was not significant. Nine fields planning was feasible for clinical practice. Conclusions For whole pelvic radiotherapy for post-hysterectomy cervical carcinoma,prone position was better than supine position for immobilization due to smaller set-up errors. The full bladder is recommended during radiotherapy, planning,For clinical practice,4 fields planning is feasible in 3DCRT while 9 fields planning is feasible in IMRT.