3-D Image-Based Radiotherapy Planning for Syed Interstitial HDR Brachytherapy in Patients with Parametrial Spread of Cervical Carcinoma

Research Article

Austin J Radiat Oncol & Cancer. 2016; 2(2): 1022.

3-D Image-Based Radiotherapy Planning for Syed Interstitial HDR Brachytherapy in Patients with Parametrial Spread of Cervical Carcinoma

Mobit PN1,2, Packianathan S1 and Yang CL1*

¹Department of Radiation Oncology, University of Mississippi Medical Center, USA

²Cameroon Oncology Center, P O Box 1870, Douala, Cameroon

*Corresponding author: Yang CL, Department of Radiation Oncology, University of Mississippi Medical Center, 350 West Woodrow Wilson Ave., Jackson, MS 39213, USA

Received: September 23, 2016; Accepted: November 02, 2016; Published: November 04, 2016


Objective: To investigate some practical issues involved in multi-fraction Syed interstitial HDR brachytherapy for patients with cervical carcinoma.

Methods: Between 8/2009 and 10/2010, eight such patients were treated at our facility with this technique. The high risk CTV (HRCTV), intermediate risk CTV (IRCTV), and organs at risk (OAR: rectum, bladder, sigmoid, and small bowel) were contoured on the planning CT images. All patients received 7 fractions of 4.2Gy prescribed to HRCTV, administered over 4 days. Planning objectives included: doses to OARs were kept below 80% of prescription dose, D90 for HRCTV = 90% of prescription dose, and V150 and V200 = 50% and 20%, respectively. OAR doses were evaluated using the dose to 2mL (D2 mL).

Results: An average of 2.4 treatment plans per patient was required to treat all fractions. The average dose to 2 mL (D2 mL) of the bladder was 63% ± 5% (1SD) of the prescription dose (29.4Gy). This value for the rectum was 64% ± 3.4%. The D2 mL values for sigmoid and small bowel were less than 40% of 29.4Gy. The D90 for HRCTV was on average 31.7Gy, whereas the D90 for IRCTV was on average 20Gy. V150 and V200 were on average 51% and 28%, respectively.

Conclusion: The implanted needles tended to move during patient transfers to and from the inpatient room to the treatment suite so pre-treatment CT scans should be performed daily and a new treatment plan should be generated if needle movements are significant.

Keywords: Syed Interstitial Brachytherapy; HDR; Cervical Carcinoma


Many studies have suggested that High Dose Rate (HDR) brachytherapy is of comparable efficacy to Low Dose Rate (LDR) brachytherapy for patients with early to advanced stage cervical cancer [1-4]. This is in addition to providing other benefits such as reduced radiation dose to clinical personnel and customized anatomicbased planning for each applicator insertion. Many cancer centers have thus adopted HDR brachytherapy using vaginal cylinders, tandem and ovoids (T&Os), or tandem and ring (T&R) for their gynecologic cancer treatment programs. However, these applicators may not always optimally cover the lateral spread of cancer, where an interstitial implant should be considered [5].

The Cervical Cancer Brachytherapy Task Group Report was published [6] in 2012 by the American Brachytherapy Society (ABS) for general recommendations. Even though our research was performed before the publication of the report, we essentially followed their guidelines that dosimetry should be performed every time the applicators are inserted to assess the doses to the targets as well as the normal tissues. While several individual experiences have been reported for HDR brachytherapy based on solid applicators mentioned above, few such extensive studies have been reported for HDR interstitial brachytherapy for cervical cancer [1,3,7]. Although a number of studies have described and evaluated interstitial brachytherapy utilizing the LDR technique, the treatment planning in these cases did not typically involve the use of 3-D imaging dataset such as CT or MRI to assess the doses to organs at risk [8,9]. Additionally, needle movements for interstitial prostate HDR brachytherapy has been reported by many investigators in the literature [10,11]. Thus, our objective is to report in detail some of the practical issues, for instance, the frequency of reimaging and replanning involved in 3-D image-based treatment planning, and to investigate the clinical planning parameters important in multifraction Syed interstitial HDR brachytherapy for patients with locally advanced cervical carcinoma. Another motivation of this work is to evaluate the adequacy of dose coverage for lateral disease in the patient group.

Methods and Materials

Patient population

Between 8/2009 and 10/2010 eight patients were treated at our facility with Syed interstitial HDR brachytherapy for advanced cervical carcinoma. The average age of the patients was 51 years (age range 36 to 68 years). The distribution of their FIGO disease stages was as follows: IIB: 12.5%, IIIB: 50%; IVA: 25%; cuff recurrence: 12.5%. All patients already received 25 fractions of external beam radiation therapy (EBRT) at 1.8Gy per fraction to the whole pelvis followed by 3 fractions of 1.8Gy each delivered as a parametrial/ sidewall boost with a midline block. This study was approved by our institutional review board.

Operating room

Before the implant procedure, each patient underwent routine bowel preparation procedures in the morning of the procedure day. They were also kept on a clear liquid diet on the day prior to the procedure. Following induction of anesthesia, patients were positioned in the dorsal lithotomy position and a Foley catheter was asceptically placed with 7mL of contrast within the bulb and sterile draping of the operative field was completed. The cervix was visualized and 4 fiducial gold markers were inserted at the 3, 6, 9, and 12 o’clock positions on the cervix. We used the modified Syed- Neblett template for the brachytherapy needle placements. 18 to 21 flexible, plastic needles (Alpha-Omega Services Inc., Bellflower, California) were inserted into the cervix and parametria. The needles comprise a 17F flexi-guide with a female Luer adaptor and a stylet with a male Luer adaptor. A collar and O-ring were used with the template with the central core inserted into the vagina. Needles are implanted according to a tentative pre-plan that had been developed based upon the extent of disease identified at the time of diagnosis. This pre-plan is based on CT, MRI and clinical exams. The radiation oncologist would outline the volume that he would like to treat with the HDR procedures. Using this information, the physicist and the radiation oncologist would then mark the positions of the needles that would use. If more of the disease is on the left, then a few more needles would be implanted on the left side of the patient. After the needles had been implanted, the template holding the needles was then sutured flush to the perineum at 4 points. A rectal tube was also inserted into the rectum to aid in identifying the rectum on future CT scans. The patient was transferred to the post-anesthesia care unit and then transported by ambulance to the outpatient radiation oncology department, about a mile away from the main hospital.

CT simulation

At the outpatient radiation oncology department, the patients underwent a limited CT scan of the pelvis. Following the first evaluation CT scan, some needles were manually repositioned by the radiation oncologist if it was thought that they did not cover the extent of disease in the cranio-caudal direction. Once needle positions were deemed appropriate, the flexi-guide needles were glued in position at the external point where they passed through the template. Thereafter, a final CT scan was performed for brachytherapy treatment planning with slice thickness of 2mm. During any CT scanning, the plastic needles would have their individual stylets in place so as to help to be identified individually later on the CT scan.

Brachytherapy treatment planning and dose prescription

The CT data was then transferred to the Varian Brachyvision Brachytherapy Treatment Planning System for plan development. The high risk CTV (HRCTV), intermediate risk CTV (IRCTV), and organs at risk including rectum, bladder, sigmoid, and small bowel were all individually contoured. The Foley catheter balloon with the contrast media was also contoured. The contours were based on GEC-ESTRO contouring guidelines [12]. In accordance with GEC ESTRO guidelines [12], the HRCTV includes the gross tumor volume. HRCTV starts superiorly at the level of the uterine vessel where it abuts the cervical tissue. The volume includes the entirety of the cervix with coverage of the most inferior extent of vaginal disease as well as laterally to include the parametrial tissues should they be involved. Should uterine extension be visible, para-uterine tissue is also included. IRCTV is generated via 1 cm expansion beyond HRCTV with removal of volume that expanded into bladder, sigmoid colon, and the rectum. For stage IIB disease, coverage of the parametrial, uterosacral, and vaginal disease must also be included.

Following completion of the contouring, the needles were individually identified by the planning medical physicist. Because of their intrinsic flexibility, 2 or more of the flexi-guide plastic needles would sometimes overlap. Mis-identification of needles could have a significant dosimetric consequence and hence, each needle was always identified in the coronal, sagittal, and axial planes by two medical physicists prior to completion of the planning process. This constitutes part of the second check procedure implemented at our institution for this procedure. The prescription dose was 4.2Gy per fraction for 7 fractions for a total dose of 29.4Gy. Figure 1 shows the anterior-posterior and right lateral digitally reconstructed radiographs for an implanted Syed patient. It is apparent from the figure that these plastic needles would sometimes overlap and therefore increase the chances of mis-identification of needles.