Evaluation of pelvic lymph node coverage of conventional radiotherapy fields based on bony landmarks in Chinese cervical cancer patients using CT simulation

Abstract

Abstract:Objective: To evaluate the pelvic lymph node coverage of conventional pelvic fields based on bony landmarks in Chinese patients with cervical cancer by using computed tomography (CT) simulation images to contour pelvic vessels as substitutes for lymph nodes location. Methods: A retrospective review of CT simulation images and conventional pelvic radiation planning data sets was performed in 100 patients with cervical cancer at the International Federation of Gynecology and Obstetrics (FIGO) Stage IIB to IIIB in our hospital. Pelvic arteries were contoured on CT simulation images, and the outlines of conventional pelvic fields were drawn as defined by the gynecologic oncology group (GOG) after hiding the contours. The distances between the following vessel contours and field borders were measured: D 1 , the superior border of the anterior/posterior (AP) field and the bifurcation of abdominal aorta; D 2 , the ipsilateral border of the AP field and the distal end of external iliac artery; and D 3 , the anterior border of the lateral (LAT) field and the distal end of the external iliac artery. The distances were recorded as positive values if the measuring point was within the conventional pelvic fields, or they were recorded as negative values. Lymph nodes coverage was considered adequate when D 1 ≥0 mm, D 2 ≥17 mm or D 3 ≥7 mm. Results: All patients had at least 1 inadequate margin, 97 patients (97.0%) had 2, and 22 patients (22.0%) had all the 3. On the AP field, 95 patients (95%) had the measuring point, the bifurcation of the abdominal aorta, out of the field (D 1 <0 mm), and all the patients had a distance less than 17.0 mm between the distal end of the external iliac artery and ipsilateral border (D 2 <17.0 mm). On the LAT field, 24 patients (24%) had a distance less than 7.0 mm between the distal end of the external iliac artery and anterior border (D 3 <7.0 mm). Conclusion: We observed that conventional pelvic fields based on bony landmarks provided inadequate coverage of pelvic lymph nodes in our patients with cervical cancer. CT simulation may be a feasible technique for planning pelvic fields optimally and individually.

Margin evaluation of translational and rotational set-up errors in intensity modulated radiotherapy for cervical cancer

“…However, it should be awarded that this result only gave advice for cervical cancer patients without para-aortic irradiation with decent errors distribution. For patients with para-aortic irradiation, target volume was longer in superior-inferior direction, which may potentially be more susceptible due to rotational set-up errors (Zhang and Yu 2009 ).…”

Advanced Imaging Applications for Locally Advanced Cervical Cancer

“…The inadequate target coverage definitely led to insufficient dose delivery and treatment failure. The most common pattern of regional recurrence (66-97%) was at the margin of the radiation field (Zhang and Yu, 2009;Beadle et al, 2010). Therefore, by using cross sectional images (CT/MRI) radiation oncologists would have more confidence to customize the external radiation treatment fields based on the findings.…”

A study to evaluate the adequacy of pelvic lymph node coverage in carcinoma cervix patients in Indian population by conventional four field box technique using computerized tomography simulation based pelvic lymph node contouring

“…In another study conducted on 100 Chinese patients, Xiang Zhang et al, contoured pelvic vessels to evaluate the adequacy of lymph node coverage by conventional pelvic fields based on bony landmarks. 12 SThe distance between the conventional field borders and various vessel contours was measured. All patients had at least one inadequate margin, 97 patients (97.0%) had two, and 22 patients (22.0%) had all the three.…”