[Analysis of different application systems and CT-controlled planning variants in treatment of primary endometrial carcinomas. Is brachytherapy treatment of the entire uterus technically possible?]

Comparison of 2D vs. 3D Dosimetry for Rotte ‘Y’ Applicator High Dose Rate Brachytherapy for Medically Inoperable Endometrial Cancer

The purpose of our research is to compare CT-based volumetric calculations and International Commission on Radiation Units and Measurements (ICRU) reference-point estimates of radiation doses to the target volume, bladder, rectum, and sigmoid colon in patients with carcinoma of the endometrium treated with high dose rate intracavitary Rotte ‘Y’ applicator brachytherapy (HDRB). Eleven patients with cancer of the endometrium were treated with CT-compatible HDR intracavitary Rotte ‘Y’ applicators (Nucletron) and underwent post-implant pelvic CT scans with applicators in place. All patients were treated using orthogonal radiography-based planning. The dose was prescribed to uterine point (a point located 2 cm below the center of a line drawn between the tips of the two ends of the Rotte applicator extending laterally from the tandem by half the maximum uterine width), Point A, and 0.5 cm depth along the upper 3 cm vagina. CT-images were transferred to the PLATO treatment planning system version 14.2.6 and retrospectively planned for volumetric calculations. The clinical target volume (CTV) included the entire uterus, cervix, and upper 3 cm of vagina. The volumes of organs at risk (OAR) were digitized. Dwell positions were identified and registered in both the uterine tandem for each patient. For those receiving HDRB alone, the prescribed dose was 7 Gy x 5 fractions. Patients who were treated following external beam radiation therapy (EBRT) received 4Gy x 5 fractions. The interfraction interval was 6–8 hours. The DVHs were computed for the CTV, bladder, rectum, and sigmoid colon. To compare doses of OARs, 1.0 cc, 2.0 cc, and 5.0 cc volumes receiving the highest dose were calculated from DVHs. 3D optimization was done to improve target coverage and decrease dose to critical organs and compared with the 2D orthogonal radiograph-based plan. The mean of percentage of prescribed dose ± S.D to 1 cc, 2 cc, and 5 cc of the OARs of interest were as follows: Rectum 44 ± 21%, 39 ± 18%, and 33 ± 15%; bladder 104 ± 36%, 91 ± 31%, and 73.9 ± 24%; and sigmoid 124 ± 35%, 109 ± 30%, and 89 ± 25%, respectively. The corresponding dose to ICRU 38 bladder and rectal points were 98 ± 55% and 50.5 ± 32%, respectively. The mean dose to uterine point and point A were 99 ± 1.7% and 98 ± 3%, respectively. The mean CTV volume was 160 ± 89 cc with the percentage of volume getting 100% and 90% of the dose being 62 ± 12% and 68 ± 12% with 2D plan versus 57 ± 8% and 67 ± 8.9% with 3D plan. The dose to critical organs were reduced with 3D optimization for rectum, bladder, and sigmoid by 5.6% (p = 0.04), 20.6% (p = 0.02), and 26.8% (p = 0.005), respectively. Compared to the 3-D volume dose, the prescription points overestimated the dose to the target volume. The under-dosing was because of inability of two channel applicator to cover volumes in the region of the cervix and vagina. The dose to sigmoid colon was high and attention should be given to the sigmoid dose at the time of treatment planning. 3D planning helped in reducing the dose to the critical organs without compromising target coverage. Correlations with outcome are needed to better define the role of 3D dosimetry in treatment planning.

Brachytherapy in pelvic malignancies: a review for radiologists

Brachytherapy, also known as sealed source or internal radiation therapy, involves placement of a radioactive source immediately adjacent to or within tumor, thus enabling delivery of a localized high dose of radiation. Compared with external beam radiation which must first pass through non-target tissues, brachytherapy results in less radiation dose to normal tissues. In the past decade, brachytherapy use has markedly increased, thus radiologists are encountering brachytherapy devices and their associated post-treatment changes to increasing degree. This review will present a variety of brachytherapy devices that radiologists may encounter during diagnostic pelvic imaging with a focus on prostate and gynecologic malignancies. The reader will become familiar with the function, correct position, and potential complications of brachytherapy devices in an effort to improve diagnostic reporting and communication with clinicians.

Consensus statement for brachytherapy for the treatment of medically inoperable endometrial cancer

PURPOSE

The purpose of this consensus statement from the American Brachytherapy Society (ABS) is to summarize recent advances and to generate general guidelines for the management of medically inoperable endometrial cancer patients with radiation therapy.

METHODS

Recent advances in the literature were summarized and reviewed by a panel of experts. Panel members participated in a series of conference calls and were surveyed to determine their current practices and patterns. This document was reviewed and approved by the full panel, the ABS Board of Directors and the ACR Commission on Radiation Oncology.

RESULTS

A transition from two-dimensional (2D) to three-dimensional (3D) treatment planning for the definitive treatment of medically inoperable endometrial cancer is described. Magnetic resonance (MR) imaging can be used to define the gross tumor volume (GTV), clinical target volume (CTV), and the organs at risk (OARs). Brachytherapy alone can be used for medically inoperable endometrial cancer patients with clinical Stage I cancer with no lymph node involvement and no evidence of deep invasion of the myometrium on MR imaging. In the absence of MR imaging, a combined approach using external beam and brachytherapy may be considered.

CONCLUSIONS

Recent advances support the use of MR imaging and 3D planning for brachytherapy treatment for medically inoperable endometrial cancer.

Dose volume analysis of radiotherapy for inoperable patients with stage I-II endometrial carcinoma

This study aims to assess the efficacy and toxicity of definitive radiotherapy for early-stage endometrial carcinoma. The correlation between CT-based dosimetric parameters and clinical outcomes is also evaluated. Between 2002 and 2006, 10 medically inoperable patients with T1-2 endometrial carcinoma were treated with radiotherapy alone. A combination of external beam radiotherapy (EBRT) and high-dose-rate intracavitary brachytherapy (HDR-ICBT) was used for 9 patients, and one was treated with HDR-ICBT alone. Dose prescription of HDR-ICBT was determined in reference to CT images at brachytherapy, and a total dose of 22-24 Gy in 4 fractions was delivered to the outer perimeter of the uterine corpus. Dose-volume parameters of the gross tumor volume (GTV), clinical target volume (CTV), and organs at risk were assessed retrospectively using the dose-volume histograms derived from the CT image-based treatment planning system. After a median follow-up of 55 months, 9 patients were alive without evidence of recurrence. One patient died from liver cirrhosis 17 months after radiotherapy. Severe acute and late toxicities were not observed in any of the patients. Average minimum dose to 90% of GTV and CTV (D90) was 88.0 and 45.9 Gy(EQD2), respectively. The minimum dose delivered to 2 cc of the most irradiated volumes of the rectum and sigmoid colon (D(2cc)) was 78.9 and 65.9 Gy(EQD2), respectively. These patients developed Grade 1 late complications. In this study, stage I-II endometrial carcinoma was well-controlled locally with minimum late toxicity by radiotherapy alone with HDR-ICBT. 3D image-based brachytherapy may potentially deliver a sufficiently high dose to the whole tumor without significant increase in dose to surrounding normal tissues.

Pilot study in the treatment of endometrial carcinoma with 3D image–based high-dose-rate brachytherapy using modified Heyman packing: Clinical experience and dose–volume histogram analysis

PURPOSE

The aim of this study was to evaluate dose distribution within uterus (clinical target volume [CTV]) and tumor (gross tumor volume [GTV]) and the resulting clinical outcome based on systematic three-dimensional treatment planning with dose-volume adaptation. Dose-volume assessment and adaptation in organs at risk and its impact on side effects were investigated in parallel.

METHODS AND MATERIALS

Sixteen patients with either locally confined endometrial carcinoma (n = 15) or adenocarcinoma of uterus and ovaries after bilateral salpingo-oophorectomy (n = 1) were included. Heyman packing was performed with mean 11 Norman-Simon applicators (3-18). Three-dimensional treatment planning based on computed tomography (n = 29) or magnetic resonance imaging (n = 18) was done in all patients with contouring of CTV, GTV, and organs at risk. Dose-volume adaptation was achieved by dwell location and time variation (intensity modulation). Twelve patients treated with curative intent received five to seven fractions of high-dose-rate brachytherapy (7 Gy per fraction) corresponding to a total dose of 60 Gy (2 Gy per fraction and alpha/beta of 10 Gy) to the CTV. Four patients had additional external beam radiotherapy (range, 10-40 Gy). One patient had salvage brachytherapy and 3 patients were treated with palliative intent. A dose-volume histogram analysis was performed in all patients. On average, 68% of the CTV and 92% of the GTV were encompassed by the 60 Gy reference volume. Median minimum dose to 90% of CTV and GTV (D90) was 35.3 Gy and 74 Gy, respectively.

RESULTS

All patients treated with curative intent had complete remission (12/12). After a median follow-up of 47 months, 5 patients are alive without tumor. Seven patients died without tumor from intercurrent disease after median 22 months. The patient with salvage treatment had a second local recurrence after 27 months and died of endometrial carcinoma after 57 months. In patients treated with palliative intent, symptom relief was achieved. No severe acute and late side effects (Grade 3/4) were observed.

CONCLUSIONS

Sectional image-based three-dimensional treatment planning on computed tomography and magnetic resonance imaging is feasible in definitive brachytherapy of endometrial carcinoma and enables by the use of dwell time and location adaptation a sufficient coverage of GTV and major parts of CTV. Local control in this limited number of patients is excellent and rate of side effects minimal.

Image-based intracavitary brachytherapy in the treatment of inoperable uterine cancer: Individual dose specification at specific anatomical sites

PURPOSE

With advances in imaging studies, dose specification for uterine cancer can be defined at specific anatomical sites such as the myometrium or the serosal surface rather than at arbitrary points or milligram-hours. This report presents our experience with image-based brachytherapy for inoperable uterine cancer.

METHODS AND MATERIALS

Eight patients with organ-confined uterine cancer (2 Stage I GI, 3 Stage I G2, 3 Stage I G3) underwent definitive radiation therapy because of poor medical condition. All the patients underwent a CT or MRI scan of the pelvis before intracavitary application. Based on the size of the uterine cavity, a single-channel intrauterine applicator was selected for a small uterus, and a multiple-channel intrauterine applicator was used for a large uterus. A CT (n=5) or MRI (n=3) scan of the pelvis was performed with the applicator in place in addition to orthogonal pelvic films. Individualized dose specification was 75Gy to the midmyometrium and limited to 50Gy to the serosal surface of the uterus based on imaging information.

RESULTS

Four patients with Stage I G1-2 disease had intracavitary brachytherapy alone. Four patients with Stage I G2-3 disease were treated with a combination of external pelvic radiation and intracavitary brachytherapy. Six patients had low-dose-rate brachytherapy, and 2 patients had high-dose-rate brachytherapy. Five patients had single-channel intrauterine brachytherapy, and 3 patients had multiple-channel brachytherapy. Based on the measurements of the uterine wall thickness by the imaging studies, the dose specification was prescribed to 1.5 cm lateral to the central axis of the uterus in 4 patients, 2.0 cm in 3 patients, and 2.5 cm in 1 patient. The medium followup time after radiation treatment was 38 months. Six patients are alive without evidence of disease, and 2 patients died of other causes. All patients had local control without major side effects.

CONCLUSIONS

Image-based brachytherapy based on individualized dose specification at specific anatomical sites can be done easily and provides excellent local control for inoperable uterine cancer.