Elsevier

Radiotherapy and Oncology

Volume 93, Issue 2, November 2009, Pages 307-310
Radiotherapy and Oncology

Cervix cancer brachytherapy
Sigmoid dose using 3D imaging in cervical-cancer brachytherapy☆

https://doi.org/10.1016/j.radonc.2009.06.032Get rights and content

Abstract

Background and Purpose

To evaluate the proximity, variance, predictors of dose, and complications to the sigmoid in cervical-cancer brachytherapy using 3D planning.

Materials and methods

Over 36 months, 50 patients were treated for cervical cancer with either low-dose-rate (LDR) or high-dose-rate (HDR) brachytherapy. The distance from the central tandem to the sigmoid, the D0.1cc and the D2cc to the sigmoid, rectum and bladder doses, and toxicity were analyzed.

Results

The median sigmoid EQD2 D0.1cc and D2cc were 84 Gy and 68.3 Gy for HDR versus 71.1 Gy and 65.9 Gy for LDR (p = 0.02 and 0.98, respectively). Twenty percent of the HDR fractions required manipulation of the superior dwell positions to decrease the sigmoid dose. The median distance from the sigmoid to the tandem was 1.7 cm (range [rg], 0.1–6.16 cm) for HDR and 2.7 cm (rg, 1.17–4.52 cm) for LDR; from the sigmoid to the 100% isodose region the median distances were −0.1 cm (rg, −1.4 to 2.5 cm) and 0.44 cm (rg. −0.73–5.2 cm), respectively. The proximity of the sigmoid to the tandem is significantly related to sigmoid dose (p < 0.0001). Within-patient (among-fraction) variation in sigmoid-to-tandem distance during HDR was substantial (coefficient of variation =40%). No grade 3–4 sigmoid toxicity was seen after a median 31-month follow-up period.

Conclusions

3D imaging in cervical-cancer brachytherapy shows the sigmoid in close proximity to the tandem. The sigmoid-to-tandem distance varies substantially between fractions, indicating the importance of sigmoid dose-volume evaluation with each fraction.

Section snippets

Patients

We conducted a retrospective review of all biopsy-confirmed cervical-cancer patients treated using 3D planning techniques with curative intent from April, 2004 to December, 2007 at the Brigham and Women’s (BWH)/Dana-Farber Cancer Center after approval by the Human Subjects Research Committee. Exclusions included one patient who had a supracervical hysterectomy treated with a short tandem and another patient treated with BT alone for Stage IB1 cervical cancer. Fifty patients were identified who

Results

A total of 170 HDR fractions were delivered to 34 patients with tandem and ovoid (17 patients), tandem and ring (5 patients), tandem and cylinder (2 patients), or a combination (10 patients). Twenty-four LDR fractions were delivered to 16 patients with tandem and ovoid (5 patients), tandem and interstitial (8 patients), or both (3 patients). Table 1 lists patient and tumor characteristics. Proportionally more Stages III and IVA patients received LDR radiation than HDR. There was no difference

Discussion

Using 3D imaging to analyze the dose delivered, this study classifies the sigmoid as an OAR. We found that the distance of the sigmoid relative to the tandem was significantly related to sigmoid dose. This study indicates that the relation of the sigmoid colon to the tandem changes between fractions, with a possible variance in the same patient of approximately 40%. It is important to note that this variance is determined by the proximity of the highest-dose region to the sigmoid, which may be

Conclusions

3D imaging in cervical-cancer brachytherapy shows the sigmoid in close proximity to the tandem. The maximum sigmoid dose is significantly related to its proximity to the tandem, which varies significantly between fractions, indicating the importance of sigmoid dose-volume evaluation with each fraction. Long-term follow-up is necessary with clinical correlation of the dose–volume relationship of the sigmoid.

Acknowledgements

We thank Eric Macklin, Ph.D. for reviewing and commenting on the statistical sections of the paper.

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    ☆

    Presented at the American Society for Therapeutic Radiology and Oncology Annual Meeting, Philadelphia, PA, November 7, 2006.

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