|Year : 2020 | Volume
| Issue : 3 | Page : 90-93
Intracavitary plesiotherapy as boost treatment in a patient of cancer cervix
Gopal Pemmaraju, Anuradha Singh, Anand Parab
Department of Advanced Centre for Radiation Oncology, Dr. Balabhai Nanavati Superspeciality Hospital, Mumbai, Maharashtra, India
|Date of Submission||30-Jun-2020|
|Date of Acceptance||04-Jul-2020|
|Date of Web Publication||29-Sep-2020|
Dr. Gopal Pemmaraju
Department of Advanced Centre for Radiation Oncology, Dr. Balabhai Nanavati Superspeciality Hospital, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
Purpose: Mold brachytherapy is an age old treatment for superficial tumors. Vaginal mold brachytherapy for gynecological malignancies of vaginal vault and vagina is being practiced in different institutes across the globe. We are reporting the technical aspects of vaginal mold and optimal treatment to the patient. Materials and Methods: This is a case of Carcinoma Cervix International Federation of Gynaecology and Obstetrics st-IIIA(lower one-third vaginal involvement) with residual disease in the anterior wall of lowerd one-third of vagina after the completion of external beam radiotherapy. The patient was reluctant for interstitial implant brachytherapy and hence was planned for vaginal mold brachytherapy with an aim to boost residual tumor. Five stainless steel Implant needles attached to the sorbo from 9'o clock to 3'o clock position with adequate spacing between the needles. Modeling wax, which is nearly tissue equivalent, was used for making mold. The material was molded into a cast cylindrically over the needles and sorbo homogeneously taking care that there were no air gaps. After taking aseptic precautions the cylindrical mold with needles and sorbo was inserted into the vaginal cavity and stabilized with a T-bandage. Computed tomography scan was performed and images were imported to treatment planning system. Clinical target volume was contoured along with organs at risk (bladder and rectum) and geometric optimization was done to obtain proper dwell times and positions where the D90was kept at 100% of the prescribed dose. Conclusion: Vaginal mold brachytherapy may be used as an alternative technique to interstitial implant brachytherapy as a boost treatment in vaginal malignancies. Patient-specific mold brachytherapy technique can be used in the cases where the target volume is superficial and limited to vagina. It is a minimally invasive technique which mimics the dose distribution of interstitial brachytherapy.
Keywords: Clinical target volume, external beam radiotherapy, high-dose rate, international federation of gynecology and obstetrics, organs at risk
|How to cite this article:|
Pemmaraju G, Singh A, Parab A. Intracavitary plesiotherapy as boost treatment in a patient of cancer cervix. J Radiat Cancer Res 2020;11:90-3
| Introduction|| |
Role of brachytherapy in the treatment of carcinoma cervix has remained a gold standard technique with improved disease control and disease-free survival in International Federation of Gynaecology and Obstetrics (FIGO) stages IB2- IVA. External beam radiotherapy (EBRT) plus brachytherapy with concurrent chemotherapy has been a standard of treatment in cervical cancers. High dose (>80 Gy) can be delivered safely to tumor with less toxicities to organs at risk (OARs) with the use of brachytherapy. Interstitial implant brachytherapy is indicated in cancer cervix with lower vaginal involvement, gross residual disease after completion of EBRT, large tumors, narrow vaginal cavity, and pelvic side wall disease.
Radium therapy was the only form of brachytherapy which began with surface applications using radium plaques and molds for squamous cell and basal cell carcinomas. First successful treatment using this technique was done in 1899.
Mold brachytherapy is an age old treatment for superficial tumors. The surface mold brachytherapy is established as a treatment option for cancers of skin. Vaginal mold brachytherapy for gynecological malignancies of vaginal vault and vagina is being practiced in different institutes across the globe. High-dose rate HDR brachytherapy offers a rapid dose fall and it is essential to mention that the applicator lies in contact with the tumor to prevent under dosage and undesired dose to OARs.
Proper material selection is crucial in designing a vaginal mold. The impression material should maintain dimensional stability, should be nontoxic, easy to cast, user friendly, cost-effective, and should be or near tissue equivalent. Different centers have made their own choice of mold material such as friction, silicone rubber, and acrylic applicator.
Catheter/needles positioning for surface mold should be done taking into consideration the target volume (tumor shape and dimensions), tumor topography, and anatomy of the patient. Image guidance with computed tomography (CT) scan in vaginal brachytherapy can be used for localization of tumor, delineating target volume, and accurate plan optimization in a desired way.
| Case Report|| |
This a case report of Carcinoma Cervix FIGO st-IIIA(lower one-third vaginal involvement) with residual disease in the anterior wall of lower one-third of vagina after the completion of EBRT. The patient was reluctant for interstitial implant brachytherapy and hence was planned for vaginal mold brachytherapy with an aim to boost residual tumor and spare OARs. The patient was examined clinically and selection of 2 cm diameter sorbo was made.
Five stainless steel Implant needles each of 1.65 mm diameter were attached to the sorbo with the help of micropore tape from 9'o clock to 3'o clock position with a spacing of 1 centimeter between each needle with their ends reaching up to tip of the sorbo.
Modeling wax, which is nearly tissue equivalent, was used for making mold. The material is available in the form of thin sheets of variable dimensions and 1 mm thickness. The sheets were immersed in hot water at 70°C for 1–2 min so that the material gets softened and can be molded to the desired shape. The material was molded into a cast cylindrically over the needles and sorbo homogeneously taking care that there were no air gaps. After taking asceptic precautions, the cylindrical mold with needles and sorbo was inserted into the vaginal cavity and stabilized with a T-bandage. CT scan was performed and images were imported to treatment planning system. Clinical target volume was contoured along with OARs (bladder and rectum) and geometric optimization was done to obtain proper dwell times and positions where the D90 was kept at 100% of the prescribed dose. Isodose shaping optimization was used to conform the dose to the target volumes without the use of optimization dose points. The optimized plan was delivered using Varian GammaMed Plus IX HDR after loader brachytherapy system having Irridium192 source with an activity of 2.936 Ci to a dose of 800 cGy X 2 fractions with 1 week interval in between the fractions.
In the present case, patient-specific vaginal mold applicator [Figure 1] and [Figure 2] was required to achieve desired dose coverage to the target volume which could not be achieved using the conventional cylindrical sorbo applicator.
The material used here for making mold applicator, i.e., Modeling Wax was checked for dosimetric evaluation. Output measurements were performed using Modeling Wax and results were compared with those using PMMA slabs with 0.6 cc Ionization Chamber.
Results were found to be in the range of 2.5%–3.0%.
Treatment Planning System used for dose calculation is Brachyvision from M/s. Varian, USA which used the American Association of Physicists in Medicine Task Group report TG-43 for dose calculations.
First point optimization was done and then manual dose shaping tool available in Brachyvision was utilized to obtain desired shape of isodose lines around the target volume. Results of manual dose shaping tool for reshaping the isodose lines were quite favorable.
[Figure 3], [Figure 4], [Figure 5] and [Table 1] show the isodose curves, encompassing the target volume planning target volume (indicated in red color) with modified peripheral needles in comparison with conventional centrally loaded source. Manual dose shaping tool was used to shift the isodose curves to achieve adequate target coverage isodose line shown in yellow color in the figure is 100% isodose line.
|Figure 3: Isodose comparison in axial plane - conventional stump applicator with centrally loaded source and modified stump applicator with peripheral needles for optimized dose distribution|
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|Figure 4: Isodose showing conventional stump applicator with centrally loaded source in sagittal plane|
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|Figure 5: Isodose showing modified stump applicator with peripheral needles for optimized dose distribution|
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|Table 1: Comparison of dose to planning target volume in centrally loaded conventional applicator and modified stump applicator with peripheral needles|
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Bladder and rectum are the OAR which received very less dose (<1 Gy) because of being at a sufficient distance from target volume.
| Discussion|| |
The success of vaginal mold brachytherapy depends on the material used for mold making, proper placement of catheters/needles in relation to the target volume and efficiently optimized plan. Modeling wax is user friendly, easy to cast, stable, nontoxic, cost-effective, and tissue equivalent.
This anatomically optimized plan using patient-specific mold is delivered to the patient using the standard procedure where each needle in the mold is checked by the dummy source before delivering the actual treatment plan.
For making the treatment cost--effective to the patient, stainless steel needles were used instead of plastic catheter tubes though an increased scatter component is expected with metallic needles.
The present case can also be considered for treating with electrons, but the results would have been inferior to brachytherapy with patient specific mold because of unwanted dose to skin and urethra in case of electron treatment. In addition, it would be relatively difficult to plan the treatment with electrons because of the uneven surface.
Nilsson et al. demonstrated an increase in dosimetric control when peripheral catheters were introduced as compared to central catheters.
Sabbas et al. showed that by activating certain combinations of catheters and dwell positions a variety of areas of different sizes and shapes can be treated. By adjusting the orientation of the applicator, the curvature of the treatment surface if set in a direction perpendicular to the direction of the catheters and exposure to the surrounding patient's anatomy while the source is in transit from the after loader to the applicator is kept minimum.
The dosimetric advantage of patient specific mold is differential dosing where the target volume can be boosted and OARs can be spared.
| Conclusion|| |
Vaginal mold brachytherapy may be used as an alternative technique to interstitial implant brachytherapy as a boost treatment in vaginal malignancies. The patient needs to be assessed for tumor control and disease-free survival. Patient-specific mold brachytherapy technique can be used in the cases where the target volume is superficial and limited to vagina. It is a minimally invasive technique which mimics the dose distribution of interstitial brachytherapy.
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Conflicts of interest
There are no conflicts of interest.
| References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]