Radiotherapy in the adjuvant setting of cervical carcinoma: treatment, results, and prognostic factors

The effect of leg position on the dose distribution of intracavitary brachytherapy for cervical cancer: 3D computerised tomography plan evaluation and in vivo dosimetric study

Purpose

To evaluate the impact of leg position on the dose distribution during intracavitary brachytherapy for cervical cancer.

Patients and methods

This prospective study was performed on 11 women with cervical cancer who underwent intracavitary brachytherapy. After insertion of the brachytherapy applicator, two sets of computed tomography slices were taken including pelvis, one with straight leg and one with leg flexion position with knee support. The dose (7 Gy) was prescribed to point A. The radiotherapy plan was run on the Plato Planning Software System V14·1 to get the dose distributions. Also, rectum and bladder doses were measured for both leg positions during the treatment. The doses and volumes of organs were compared via the Wilcoxon signed-rank test by using Statistical Package for the Social Sciences 11·5 statistical software.

Results

No significant difference regarding the dose distributions and volumes of target, sigmoid and bladder due to leg position was observed, either on 3D planning or on in vivo dose measurements. However, there were significant differences for 25 and 50% isodose coverage of rectum in favour of straight leg position (p=0·026). There were no significant differences regarding maximum doses in any critical organ.

Conclusion

Difference in leg position caused only a small change in rectum dose distribution and did not cause any other change in either dose distributions or in vivo measured doses of both target and critical organs during cervical brachytherapy. Straight leg position appears better with regard to rectum dose.

Comparison of intracavitary brachytherapy and stereotactic body radiotherapy dose distribution for cervical cancer

PURPOSE

To compare the dose distribution characteristics of stereotactic body radiotherapy (SBRT) with intracavitary high-dose-rate (HDR) brachytherapy in patients with cervical carcinoma.

METHODS AND MATERIALS

HDR intracavitary brachytherapy treatment plans for 11 women with cervical carcinoma were evaluated in this analysis. The total HDR brachytherapy dose was 28Gy given in four fractions. HDR brachytherapy was delivered with the microSelectron HDR therapy unit (Nucletron B. V., Veenendaal, The Netherlands). SBRT plans for each patient were generated with MultiPlan for CyberKnife Robotic Radiosurgery System (Accuray Inc., Sunnyvale, CA). The dose distributions, dose-volume histograms, and maximum dose points of the target and critical organs were recorded for both plans.

RESULTS

SBRT yielded significantly better target coverage; the median target coverage for the 100% isodose line was 50.7% for HDR brachytherapy plans, whereas it was 99.1% for SBRT plans. The dose distributions for critical organs were similar in both types of plans. The exceptions were the 25% isodose being significantly better in brachytherapy plans for rectum, and the 100% isodose exposure being higher in brachytherapy plans for rectum, bladder, and sigmoid colon. Some significant differences were also found in maximum doses received by a 2-cc volume of bladder in favor of SBRT plans. In addition, maximum bone marrow doses were significantly higher in SBRT plans.

CONCLUSION

SBRT plans achieved better target coverage and better dose distributions to critical organs except bone marrow compared with HDR brachytherapy plans in patients with locally advanced cervical cancer.