A comparative dosimetric study of conventional, conformal and intensity-modulated radiotherapy in postoperative pelvic irradiation of cervical cancer / 中华放射肿瘤学杂志

ABSTRACT

Objective To evaluate target-volume coverage and organ at risk (OAR) protection achieved with conventional radiotherapy (CRT), three dimensional eonformal radiotherapy (3DCRT) , and intensity-modulated radiotherapy(IMRT) through dosimetric comparison in patients with cervical cancer after hysterectomy. Methods The planning CT scans of 10 patients treated with pelvic radiation after hysterectomy for cervical cancer were used to generate CRT,3DCRT and IMRT plans for this study. Clinical target volume(CTV) was contoured on the individual axial CT slices of every patient. The CTV was then uniformly expanded by 1.0 cm to create the planning target volume (PTV). The small bowel, rectum, bladder, bone marrow, ovaries, and femoral heads were outlined for the organ at risk (OAR) evaluation. The CRT ,3DCRT and IMRT plans were generated using commercial planning software. CRT plan was prescribed to deliver 45 Gy to the reference point,while IMRT and 3DCRT plans were 45 Gy to 95% of the FFV. Isodose line and dose volume histograms(DVH) were used to evaluate the dose distribution in CTV and OAR. Results For 10 patients, the average volume of CTV receiving the prescribed dose of CRT was significantly lower than 3DCRT( Q = 8.27,P ＜ 0.01 ) and IMRT( Q = 8.37, P ＜ 0.01 ), respectively. Comparing with the CRT plan,the 3DCRT and IMRT plans notably reduced the volume of bowel at 30 and 45 Gy levels. The IMRT plan significantly spared rectum and bladder at 30 and 45 Gy levels comparing with the CRT ( P ＜ 0.01 ) and 3DCRT( P ＜ 0.05 ) plans,while the 3DCRT plan significantly spared rectum and bladder at 45 Gy level comparing with the CRT( P ＜0.01 ) plans. For 4 patients with ovarian transposition, the average doses of ovary over 3 Gy were 2 patients with the 3DCRT and IMRT plans, and 2 with all three plans. Conclusions IMRT and 3DCRT are superior to CRT in improving dose coverage of target volume and sparing of OAR ,while IMRT being the best. The superiority of IMRT and 3DCRT is obvious in sparing bone marrow at high dose levels. IMRT,3DCRT and CRT could not spare the transposed ovary effectively.