Vaginal Cylinder Research Articles

The impact of air pockets around the vaginal cylinder on vaginal vault brachytherapy.

To evaluate the incidence, size and predisposing factors for air pockets around the vaginal cylinder and their dosimetric effect on the vaginal mucosa. We investigated 174 patients with endometrial carcinoma treated with external radiotherapy (RT) and brachytherapy (BRT) (101 patients, 58%) or BRT alone (73 patients, 42%). The quantity, volume and dosimetric impact of the air pockets surrounding the vaginal cylinder were quantified. The proportions of patients with or without air pockets during application were stratified according to menopausal status, treatment modality and interval between surgery and RT. Air pockets around the vaginal cylinder were seen in 75 patients (43%), while 99 patients (57%) had no air pockets. Only 11 patients (6.3%) received less than the prescribed dose (average 93.9% of prescribed dose; range, 79.0-99.2%). Air pockets were significantly fewer in pre-menopausal patients or in patients treated with the combination of external RT and BRT than in post-menopausal patients or patients treated with BRT alone. A significant correlation existed between the mucosal displacement of the air gap and the ratio of the measured dose at the surface of the air gap and prescribed dose (Pearson r = -0.775; p < 0.001). Air pockets were still a frequent problem during vaginal vault BRT, especially in post-menopausal patients or in patients treated with BRT alone, which may potentially cause dose reductions at the vaginal mucosa. Air pockets around the vaginal cylinder remain a significant problem, which may potentially cause dose reduction in the target volume.

Comparison of doses to the rectum derived from treatment planning system with in-vivo dose values in vaginal vault brachytherapy using cylinder applicators.

PurposeIn-vivo measurements to determine doses to organs-at-risk can be an essential part of brachytherapy quality assurance (QA). This study compares calculated doses to the rectum with measured dose values as a means of QA in vaginal vault brachytherapy using cylinder applicators.Material and methodsAt the Department of Radiotherapy, University College Hospital (UCH), Ibadan, Nigeria, intracavitary brachytherapy (ICBT) was delivered by a GyneSource high-dose-rate (HDR) unit with 60Co. Standard 2D treatment plans were created with HDR basic 2.6 software for prescription doses 5-7 Gy at points 5 mm away from the posterior surface of vaginal cylinder applicators (20, 25, and 30 mm diameters). The LiF:Mg, Ti thermoluminescent dosimeter rods (1 x 6 mm) were irradiated to a dose of 7 Gy on Theratron 60Co machine for calibration purpose prior to clinical use. Measurements in each of 34 insertions involving fourteen patients were performed with 5 TLD-100 rods placed along a re-usable rectal marker positioned in the rectum. The dosimeters were read in Harshaw 3500 TLD reader and compared with doses derived from the treatment planning system (TPS) at 1 cm away from the dose prescription points.ResultsThe mean calculated and measured doses ranged from 2.1-3.8 Gy and 1.2-5.6 Gy with averages of 3.0 ± 0.5 Gy and 3.1 ± 1.1 Gy, respectively, for treatment lengths 2-8 cm along the cylinder-applicators. The mean values correspond to 48.9% and 50.8% of the prescribed doses, respectively. The deviations of the mean in-vivo doses from the TPS values ranged from –1.9 to 2.1 Gy with a p-value of 0.427.ConclusionsThis study was part of efforts to verify rectal dose obtained from the TPS during vaginal vault brachytherapy. There was no significant difference in the dose to the rectum from the two methods of measurements.

Is there a subset of patients with recurrent cancer in the vagina who are not candidates for interstitial brachytherapy that can be treated with multichannel vaginal brachytherapy using graphic optimization?

PurposeTo evaluate recurrent vaginal cancer treated with vaginal brachytherapy (VBT) using graphic optimization in patients not amenable to surgery and interstitial brachytherapy (ISBT).Material and methodsWe retrospectively reviewed the records of 5 patients with recurrent cancer in the vagina that were deemed not to be good candidates for ISBT implant because of medical reasons. All patients received computed tomography/magnetic resonance imaging (CT/MRI) based evaluation in addition to a detailed clinical examination, and were noted to have recurrent nodules in the vagina with size ranging from 10-25 mm. Four of the 5 patients had recurrent disease in the vaginal apex, whereas one patient had recurrence in the lateral vaginal wall. Subsequently, all patients were treated with external beam radiation therapy (EBRT) followed by multichannel vaginal cylinder (MVC)-based VBT using graphic optimization for shaping the isodose to improve the clinical target volume (CTV) coverage, as well as to spare the organs at risk (OAR). The dose to the bladder and rectum with regard to 0.1 cc, 1 cc, and 2 cc were recorded.ResultsMedian age of the patients was 78 years (range 58-86 years). Thickness of the lesions before VBT ranged from 6-15 mm. All patients were followed up with MRI at 3 months. All patients but one demonstrated complete clinical/ radiological response of the tumor. No patient had any grade III/IV toxicity at 24 months.ConclusionsMVC-based VBT using graphic optimization is safe and yields favorable results if used judiciously.

Bladder and rectum dose estimations on digitized radiographs for vaginal brachytherapy after hysterectomy.

The purpose of this study was to evaluate the feasibility of assessing bladder and rectal point doses, using orthogonal radiographs without treatment planning, for vaginal cylinder applicator (VC), high‐dose‐rate (HDR) vaginal cuff brachytherapy (BT) after hysterectomy. Thirty‐three VC HDR BT treatment plans from 31 postoperative endometrial cancer patients were retrospectively analyzed. Single‐channel VC with four differing diameters — 2.0 cm, 2.3 cm, 2.6 cm, and 3.0 cm — were analyzed. Dose‐distance modeling was performed to estimate bladder and rectal point doses by measuring distances on each orthogonal radiograph without treatment planning. The estimated doses were then compared with doses calculated on treatment planning system (TPS). Their percent (%) dose differences were recorded. Analysis was performed for each VC size, ICRU bladder and rectal points, and the closest rectal point. The estimated doses obtained from dose‐distance modeling displayed on average less than 2.5% difference when compared with TPS doses at ICRU bladder and rectal points for each VC size. Dose percent differences between estimated values and TPS values were on average 1.9% and 2.5% for ICRU bladder and rectal point, respectively, regardless of VC sizes. Dose‐distance modeling for closest rectal point presented on average 5.4% dose difference when compared with TPS values of all VC sizes. It was feasible to estimate rectal and bladder point doses by measuring distances on orthogonal radiographs without treatment planning. Percent dose differences were 2.5% less for both ICRU bladder and rectal points, regardless of VC sizes. The use of closest rectal point is not recommended for estimating rectal dose.PACS number: 87.53.‐j, 87.53.Jw, 87.55.‐x, 87.55.D‐, 87.55dk

Comparison of Target Volume and Organ at Risk Doses With Multi-channel Versus Single Channel Cylinder for Vaginal Brachytherapy

Purpose/Objective(s)Postoperative vaginal brachytherapy is used in intermediate and high risk endometrial cancer patients either alone or after pelvic irradiation. We aimed to assess the dosimetric parameters of a multi-channel vaginal cylinder applicator compared to traditional single channel cylinder for vaginal brachytherapy.Materials/MethodsTen patients were treated with multi-channel cylinder using the 6 peripheral channels. Single channel plans were generated for comparison. CTV was defined as 5 mm lateral and 3 mm AP volumetric expansion of the cylinder. The prescription dose was 5.5 Gy to CTV for each of 5 fractions. Plans were optimized to achieve D90>100% for CTV. Both plans were compared for D5cc, D2cc, D1cc and D0.1 cc of rectum and the bladder.ResultsThe vaginal cylinder diameters ranged from 3 to 3.5 cm, and the active source lengths ranged from 3 to 4 cm. Mean CTV D90 values were 104% for single channel and 105% (p = 0.53) for multichannel plans. The rectal D5cc, D2cc, D1cc and D 0.1cc doses were reduced by 7.2% (p<0.001), 6.2% (p = 0.001), 7.3% (p = 0.003) and 3.3% (p = 0.233), respectively in multi-channel plans compared to single channel plans. Similarly, the bladder doses were reduced by 11.4% (p = 0.001), 12.4% (p = 0.004), 13.8% (p = 0.031) and 20.5% (p = 0.153), respectively.ConclusionsVaginal brachytherapy with multi-channel cylinder is able to provide similar target volume coverage and a better organ at risk sparing in asymmetrical CTVs. Purpose/Objective(s)Postoperative vaginal brachytherapy is used in intermediate and high risk endometrial cancer patients either alone or after pelvic irradiation. We aimed to assess the dosimetric parameters of a multi-channel vaginal cylinder applicator compared to traditional single channel cylinder for vaginal brachytherapy. Postoperative vaginal brachytherapy is used in intermediate and high risk endometrial cancer patients either alone or after pelvic irradiation. We aimed to assess the dosimetric parameters of a multi-channel vaginal cylinder applicator compared to traditional single channel cylinder for vaginal brachytherapy. Materials/MethodsTen patients were treated with multi-channel cylinder using the 6 peripheral channels. Single channel plans were generated for comparison. CTV was defined as 5 mm lateral and 3 mm AP volumetric expansion of the cylinder. The prescription dose was 5.5 Gy to CTV for each of 5 fractions. Plans were optimized to achieve D90>100% for CTV. Both plans were compared for D5cc, D2cc, D1cc and D0.1 cc of rectum and the bladder. Ten patients were treated with multi-channel cylinder using the 6 peripheral channels. Single channel plans were generated for comparison. CTV was defined as 5 mm lateral and 3 mm AP volumetric expansion of the cylinder. The prescription dose was 5.5 Gy to CTV for each of 5 fractions. Plans were optimized to achieve D90>100% for CTV. Both plans were compared for D5cc, D2cc, D1cc and D0.1 cc of rectum and the bladder. ResultsThe vaginal cylinder diameters ranged from 3 to 3.5 cm, and the active source lengths ranged from 3 to 4 cm. Mean CTV D90 values were 104% for single channel and 105% (p = 0.53) for multichannel plans. The rectal D5cc, D2cc, D1cc and D 0.1cc doses were reduced by 7.2% (p<0.001), 6.2% (p = 0.001), 7.3% (p = 0.003) and 3.3% (p = 0.233), respectively in multi-channel plans compared to single channel plans. Similarly, the bladder doses were reduced by 11.4% (p = 0.001), 12.4% (p = 0.004), 13.8% (p = 0.031) and 20.5% (p = 0.153), respectively. The vaginal cylinder diameters ranged from 3 to 3.5 cm, and the active source lengths ranged from 3 to 4 cm. Mean CTV D90 values were 104% for single channel and 105% (p = 0.53) for multichannel plans. The rectal D5cc, D2cc, D1cc and D 0.1cc doses were reduced by 7.2% (p<0.001), 6.2% (p = 0.001), 7.3% (p = 0.003) and 3.3% (p = 0.233), respectively in multi-channel plans compared to single channel plans. Similarly, the bladder doses were reduced by 11.4% (p = 0.001), 12.4% (p = 0.004), 13.8% (p = 0.031) and 20.5% (p = 0.153), respectively. ConclusionsVaginal brachytherapy with multi-channel cylinder is able to provide similar target volume coverage and a better organ at risk sparing in asymmetrical CTVs. Vaginal brachytherapy with multi-channel cylinder is able to provide similar target volume coverage and a better organ at risk sparing in asymmetrical CTVs.

Assessing the Need for Dose Calculations to Organs at Risk Using MRI Planning in Vaginal Brachytherapy

With the overall low morbidity of adjuvant vaginal brachytherapy (VB) and its relatively fixed geometry, the need for individual calculation of doses to organs at risk (OARs) such as the bladder and rectum has been questioned, and ICRU bladder and rectal point dose calculations have been previously recommended. Using T1 and T2-weighted MRI simulation scans during VB, we evaluated patient anatomic variability and doses to OARs. Nineteen MRI simulation scans from 9 endometrial cancer patients undergoing adjuvant VB were obtained. In this retrospective study, all cases were planned to treat the proximal 4cm of vagina to a total dose of 21 Gy in 3 fractions prescribed to 5mm. The urethra, bladder, rectum, and sigmoid were contoured and the minimum dose in Gy to the most exposed 0.1cc, 1cc, and 2cc of the organ (D0.1cc, D1cc, D2cc) and the ICRU 38 bladder and rectal points were calculated. Additionally, patient anatomic variability in relation to OARs was assessed. The mean D2cc to the bladder, sigmoid, and rectum per 7Gy treatment fraction prescribed to 5mm were 5.6 Gy (3.3 - 7.32 Gy), 2.4 Gy (0.6 - 5.9 Gy), and 6.0 Gy (4.1 - 7.1 Gy), respectively. The mean D0.1cc to the urethra was 5.2 Gy (2.0 - 7.7 Gy). MRI scans revealed that significant variability can exist in the dose to the sigmoid colon, especially when positioned superiorly at the apex of the vaginal cylinder. Due to the anatomy of the internal urethral sphincter, the urethra deviates from the bowel at the location of the vaginal vault. However, even when treating the proximal 4cm of the vagina, the D0.1cc urethra exceeds 75% and 100% of the prescription dose in 36.8% and 15.8% of cases, respectively. The bladder and rectal ICRU points underestimated D0.1cc to their respective structures by more than 10% of the prescription dose in 68.4% and 78.9% of cases, respectively. An initial MRI simulation scan may guide VB treatment regarding vaginal length and prescription (surface or 5mm) relative to the location of critical structures. In cases when bowel is located above the vaginal apex, or the urethral point dose approaches the prescription dose, a more prolonged treatment course and prescription to the vaginal surface can be considered. Based on this study, it appears that the ICRU bladder and rectum points underestimate the dose to 0.1cc of the organ by greater than 10% of the prescription dose in most cases.

Determination of Standardized Objective and Constraint Settings for Inverse Planning Using IPSA and HIPO for HDR Brachytherapy Multichannel Vaginal Cylinders

Determination of Standardized Objective and Constraint Settings for Inverse Planning Using IPSA and HIPO for HDR Brachytherapy Multichannel Vaginal Cylinders

An investigation of a PRESAGE® in vivo dosimeter for brachytherapy

Determining accurate in vivo dosimetry in brachytherapy treatment with high dose gradients is challenging. Here we introduce, investigate, and characterize a novel in vivo dosimeter and readout technique with the potential to address this problem. A cylindrical (4 mm × 20 mm) tissue equivalent radiochromic dosimeter PRESAGE® in vivo (PRESAGE®-IV) is investigated. Two readout methods of the radiation induced change in optical density (OD) were investigated: (i) volume-averaged readout by spectrophotometer, and (ii) a line profile readout by 2D projection imaging utilizing a high-resolution (50 micron) telecentric optical system. Method (i) is considered the gold standard when applied to PRESAGE® in optical cuvettes. The feasibility of both methods was evaluated by comparison to standard measurements on PRESAGE® in optical cuvettes via spectrophotometer. An end-to-end feasibility study was performed by a side-by-side comparison with TLDs in an 192Ir HDR delivery. 7 and 8 Gy was delivered to PRESAGE®-IV and TLDs attached to the surface of a vaginal cylinder. Known geometry enabled direct comparison of measured dose with a commissioned treatment planning system. A high-resolution readout study under a steep dose gradient region showed 98.9% (5%/1 mm) agreement between PRESAGE®-IV and Gafchromic® EBT2 Film. Spectrometer measurements exhibited a linear dose response between 0–15 Gy with sensitivity of 0.0133 ± 0.0007 ΔOD/(Gy ⋅ cm) at the 95% confidence interval. Method (ii) yielded a linear response with sensitivity of 0.0132 ± 0.0006 (ΔOD/Gy), within 2% of method (i). Method (i) has poor spatial resolution due to volume averaging. Method (ii) has higher resolution (∼1 mm) without loss of sensitivity or increased noise. Both readout methods are shown to be feasible. The end-to-end comparison revealed a 2.5% agreement between PRESAGE®-IV and treatment plan in regions of uniform high dose. PRESAGE®-IV shows promise for in vivo dose verification, although improved sensitivity would be desirable. Advantages include high-resolution, convenience and fast, low-cost readout.

Three-dimensional dosimetry of the full and empty bladder in high dose rate vaginal cuff brachytherapy.

The objectives of the study were to assess the bladder doses during vaginal cuff brachytherapy and to examine the effect of bladder filling on normal tissue dosimetry by means of computed tomography. A total number of 45 women were enrolled in a prospective clinical trial. Patients were treated with the application of a single-line source vaginal cylinder. All the patients were asked to consume 400 mL of water 40 minutes before computed tomography scans were taken. For each patient, 2 treatment plans were performed-one with full bladder and the other one when the bladder was emptied. A dose-volume histogram and the equivalent of 2-Gy dose for full and empty bladder were calculated. Doses to the bowels in 2 states of the bladder were estimated. Thirty-five patients received a lower dose to the empty bladder than to the filled organ. The average dose difference was 0.5 Gy. Ten patients received a lower dose to the full bladder than to the empty one. However, in this case, the difference amounted only to 0.2 Gy on average. Dose parameters (the maximal dose received by 0.1 cm of tissue and the maximal dose received by 2 cm of tissue) were lower in the empty state, but the volumetric parameters (the percent of bladder volume receiving ≥50% of the prescribed dose and the percent of bladder volume receiving ≥80% of the prescribed dose) were higher in the empty state of the bladder. Doses to the bowels seemed to be higher in the empty bladder. However, none of the doses exceeded the limitations. The results have shown that in most cases, the dose to the empty bladder is lower than when the bladder is full. Simultaneously, the doses to the bowels increase proportionally in the empty state of the bladder comparing to the full organ. Protection of the bowels, which are more radiosensitive, suggests treating the patients in the full state of the bladder. Early and late bowel toxicity should be investigated to establish clear standards of treatment.

WE-F-16A-01: Commissioning and Clinical Use of PC-ISO for Customized, 3D Printed, Gynecological Brachytherapy Applicators

Purpose: (1) Evaluate the safety and radiation attenuation properties of PCISO, a bio-compatible, sterilizable 3D printing material by Stratasys, (2) establish a method for commissioning customized multi- and single-use 3D printed applicators, (3) report on use of customized vaginal cylinders used to treat a series of serous endometrial cancer patient. Methods: A custom film dosimetry apparatus was designed to hold a Gafchromic radio film segment between two blocks of PC-ISO and 3D-printed using a Fortus 400mc (StrataSys). A dose plan was computed using 13 dwell positions at 2.5 mm spacing and normalized to 1500 cGy at 1 cm. Film exposure was compared to control tests in only air and only water. The average Hounsfield Unit (HU) was computed and used to verify water equivalency. For the clinical use cases, the physician specifies the dimensions and geometry of a custom applicator from which a CAD model is designed and printed. Results: The doses measured from the PC-ISO Gafchromic film test were within 1% of the dose measured in only water between 1cm and 6cm from the channel. Doses increased 7–4% measured in only air. HU range was 11–43. The applicators were sterilized using the Sterrad system multiple times without damage. As of submission 3 unique cylinders have been designed, printed, and used in the clinic. A standardizable workflow for commissioning custom 3D printed applicators was codified and will be reported. Conclusions: Quality assurance (QA) evaluation of the PC-ISO 3D-printing material showed that PC-ISO is a suitable material for a gynecological brachytherapy vaginal cylinder in a clinical setting. With the material commissioning completed, if the physician determines that a better treatment would Result, a customized design is fabricated with limited additional QA necessary. Although this study was specific to PC-ISO, the same setup can be used to evaluate other 3D-printing materials.

Uterine Carcinosarcoma Confined to the Pelvis: A Retrospective Review and Outcome Analysis

Objective. We compared the treatments of uterine carcinosarcoma at our institution and evaluated their impact on survival. Methods. A retrospective analysis was performed on 60 eligible patients with carcinosarcoma limited to the pelvis. Subjects were divided into four categories: surgery, surgery plus chemotherapy, surgery plus radiation therapy, and a combination of surgery, chemotherapy, and RT. The most commonly used chemotherapy was cisplatin and/or carboplatin and taxol. Radiotherapy included external beam radiation therapy (EBRT) alone or with high dose rate (HDR) brachytherapy or HDR brachytherapy alone. Survival probability data were computed using the Kaplan-Meier method. The differences between groups were compared using the log-rank test. Results. The combination of surgery and radiation therapy with or without chemotherapy is seen to improve overall survival (OS) compared to surgery alone (P=0.044 and P=0.028, resp.). Brachytherapy involving three HDR vaginal cylinder fractions shows an equally effective reduction in local recurrence compared to EBRT. Conclusion. Our study of a relatively large number of carcinosarcoma patients suggests that adjuvant radiation therapy improves OS compared to surgery alone. Brachytherapy with 3 HDR vaginal cylinder fractions is preferred because of its time-saving, better tolerance, low toxicity and equivalent OS, and local control compared to EBRT.

Clinical Outcomes for 3-Dimensional High-Dose-Rate Vaginal Brachytherapy Using an Intravaginal Multichannel Cylinder: Improving Dosimetry to Decrease Toxicity for Primary and Recurrent Vaginal Cancers

Brachytherapy is an integral part of vaginal cancer treatment, delivered via either interstitial or a standard single-channel vaginal cylinder applicator. Recently, we along with others have published dosimetric studies showing improved organ-at-risk (OAR) sparing with a multichannel vaginal cylinder over the standard single-channel applicator. However, whether these dosimetric advantages afforded by a multi-channel cylinder applicator translate into clinical meaningful outcomes is unknown.

A Custom-made Urethral Applicator for High-Dose-Rate Brachytherapy in Advanced Vaginal Cancer

Urethral extension in vaginal cancer presents a difficult area to treat effectively and without complication. After pelvic irradiation, gross disease in this region may be boosted externally or preferably with HDR brachytherapy. However, depending on the depth and positioning of the lesion, a single or multi-channel vaginal cylinder may not effectively target the area. An interstitial template can be considered, but carries additional procedural risk. In this study, we present the case of a patient with locally advanced vaginal cancer with significant periurethral extension, effectively treated with a custom urethral brachytherapy applicator built from common components.

Dosimetric Comparison of Heterogeniety Versus Nonheterogeneity Corrected Dose Calculations in Vaginal Brachytherapy: The Impact of Air Gaps

The presence of air gaps between an HDR vaginal cylinder and the vaginal wall is potentially problematic as it may push the vaginal lymphatics outside the prescribed isodose line. This prospective study compares the volume of air gaps observed for two different diameter cylinders (2 cm and optimal) inserted in the same patient and evaluates the dosimetric impact on the target volume (vaginal lymphatics) and the surrounding normal tissues using both heterogeneity and non-heterogeneity corrected calculation algorithms.

Assessment of air pockets in high-dose-rate vaginal cuff brachytherapy using cylindrical applicators.

PurposeTo retrospectively assess the incidence and magnitude of air pockets around vaginal cylinders and its impact on dose distribution in vaginal cuff image-guided high-dose-rate (HDR) brachytherapy.Material and methodsFifty endometrial carcinoma patients treated by postoperative HDR vaginal cuff brachytherapy were included in the study. The average age of patients was 58.3 ± 11.8 years (range: 31-87 years). Brachytherapy was performed using cylindrical applicators, and the dose prescribed to 0.5 cm from the applicator's surface, over a length of 5 cm from the applicator's tip. Computed tomography (CT) simulation was used for each brachytherapy fraction. The incidence, vaginal mucosa displacement, volume, and dosimetric effect of air pockets around the vaginal cylinder were evaluated.ResultsA total of 78 air pockets were found in 29/50 patients (58%) and 45/135 (33%) brachytherapy plans. They were located at the apex: 16/78 (20%) and lateral to the applicator: 62/78 (80%). The volume of air pockets ranged between 0.01 and 2.1 cm3 (mean: 0.15 cm3 ± 0.36 cm3), and the maximum displacement of vaginal mucosa from cylinder surface was between 0.1 and 1.09 cm (mean: 0.34 cm ± 0.2 cm). The dose reduction to the vaginal mucosa generated by the air pockets ranged from 0.5 to 66% (mean: 26.4% ± 13.9%).ConclusionsThe presence of air pockets around vaginal cylinder applicators is frequently noticed in post-operative vaginal cuff brachytherapy. The dose to the vaginal mucosa is reduced, as a result of displacement generated by air pockets. The effect on the clinical outcome of this dose reduction is yet to be determined.

First clinical implementation of the Capri applicator

This study was to assess the Capri applicator for patients with endometrial cancer undergoing high‐radiation dose treatments following external‐beam radiation therapy. The Capri applicator is an inflatable vaginal cylinder with multiple channels. It is used to tailor the dose distribution to an asymmetric vaginal disease, and better spare organs at risk. Five patients with high‐risk endometrial cancer were selected for this study. The patients were treated with a high dose of radiation using the Capri applicator: daily fraction of 7 Gy was prescribed for a total dose of 21 Gy. The treatment plans included radiobiological parameters such as equivalent uniform dose (EUD), normal tissue complication probability (NTCP), and tumor control probability (TCP). Based on the dose‐volume histograms (DVH), we also calculated four quality factors: conformity index (CI), dose homogeneity index (DHI), dose nonuniformity index (DNR), and overdose index (OI). The TCP values range from 82.26% to 95.92%. Very low values of NTCP were observed for the bladder and rectum. The EUDs to organs at risk ranged from 4.65 Gy to 18.22 Gy for the bladder, and from 3.41 Gy from to 6.56 Gy for the rectum. The mean CI was 1.05(SD=0.0008). The mean DNR was 0.10(range0.0−0.295,SD=0.100). The mean OI was 0.019(SD=0.028). The DHIs were in the range of 1.0−0.754(mean0.886,SD=0.116). The use of a multichannel vaginal cylinder may not only help cover extensive vaginal disease, but also reduce the dose to the rectum. This dosimetric analysis shows that rectal doses could be reduced using a multichannel cylinder. However, the dose delivered to the bladder based on EUD calculation may be higher than that obtained with other methods. Each patient must be evaluated independently to determine if a multichannel treatment is appropriate. Clinical followup will show whether this rectal dose sparing translates into a real toxicity improvement.PACS number: 3.6.96.0

High-Dose-Rate Brachytherapy for the Treatment of Vaginal Intraepithelial Neoplasia

PurposeVaginal intraepithelial neoplasia (VAIN), a rare premalignant condition, is difficult to eradicate. We assess the effectiveness of high-dose rate intracavitary brachytherapy (HDR-ICR) in patients with VAIN or carcinoma in situ (CIS) of the vagina after hysterectomy.Materials and MethodsWe reviewed 34 patients treated for posthysterectomy VAIN or CIS of the vagina by brachytherapy as the sole treatment. All patients underwent a coloposcopic-directed punch biopsy or had abnormal cytology, at least 3 consecutive times. All patients were treated with a vaginal cylinder applicator. The total radiation dose was mainly 40 Gy in 8 fractions during the periods of 4 weeks at a prescription point of the median 0.2 cm (range, 0 to 0.5 cm) depth from the surface of the vaginal mucosa.ResultsAcute toxicity was minimal. Seven patients had grade 1/2 acute urinary and rectal complications. There were 15 cases of late toxicity, predominantly vaginal mucosal reaction in 12 patients. Of these patients, two patients suffered from grade 3 vaginal stricture and dyspareunia continuously. After a median follow-up time of 48 months (range, 4 to 122 months), there were 2 recurrences and 2 persistent diseases, in which a second-line therapy was needed. The success rate was 88.2%. The average prescription point in failure patients was 1.1 mm from the surface of the vagina compared to an average of 2.6 mm in non-recurrent patients (p=0.097).ConclusionHDR-ICR is an effective treatment method in VAIN patients. In spite of high cure rates, we should consider issues regarding vaginal toxicity and radiation techniques to reduce the occurrence of failure and toxicity.

PO-1013: Multichannel vaginal cylinder: Interfraction rotational variation and its dosimetric impact

PO-1013: Multichannel vaginal cylinder: Interfraction rotational variation and its dosimetric impact

Evaluating adjacent organ radiation doses from postoperative intracavitary vaginal vault brachytherapy for endometrial cancer

To document doses received by critical organs during adjuvant high-dose-rate (HDR) vaginal vault brachytherapy. Patients treated with HDR vaginal vault radiation between January 1, 2009, and January 31, 2012, who had a CT simulation with the treatment cylinder in situ were included. The CT scans were retrospectively reviewed and the rectum, sigmoid, small bowel, and bladder were contoured. Standardized plans treating the upper 4 cm of the vaginal vault were used to deliver a total of 21 Gy (Gy) at 0.5 cm from the apex of the vaginal vault in three fractions. There were 41 patients. Median age was 62 years. The median vaginal cylinder diameter was 3 cm. The mean 2cc dose to the rectum, sigmoid, small bowel, and bladder were 5.7, 4.7, 4.0, and 5.6 Gy, respectively. Bladder volume ranged from 67-797cc. Assuming minimal interfraction organ variation, the equivalent dose in 2 Gy/fraction was extrapolated from data and may be near or beyond organ tolerance for rectum, sigmoid, and small bowel in some cases. Spearman correlation found that increased bladder volume was not associated with adjacent organs at risk dose but may be associated with a trend (p=0.06) toward increased bladder dose (R=0.30). This study describes the dose received by adjacent critical structures during vaginal vault HDR brachytherapy. This is important information for documentation in the rare setting of treatment-related toxicity or recurrence. Bladder volume was not associated with dose to adjacent organs.

Dosimetric comparison of multichannel with one single-channel vaginal cylinder for vaginal cancer treatments with high-dose-rate brachytherapy

To compare the three-dimensional (3D) image (CT/MR)-based planning with a multichannel vaginal cylinder (MVC) to a single-channel vaginal cylinder (SVC) for the treatment of vaginal cancer. A total of 20 consecutive patients were treated with 3D CT/MR image-based high-dose-rate (HDR) brachytherapy using an MVC. All patients received external beam radiation therapy before HDR brachytherapy. A brachytherapy dose of 20-25Gy of more than five fractions was delivered to clinical target volume (CTV). Retrospectively, treatment plans for all patients were generated using the central channel only to mimic an SVC applicator. The SVC plans were optimized to match CTV coverage with MVC plans. Dose homogeneity index as well as bladder, rectum, sigmoid, and urethral doses were compared. The mean D90 for CTV was 74.2Gy (range: 48.8-84.1Gy). The mean (±standard deviation) of dose homogeneity index for MVC vs. SVC was 0.49 (±0.19) and 0.52 (±0.23), respectively (p=0.09). Mean bladder 0.1, 1, and 2cc doses for MVC vs. SVC were 69 vs. 71.2Gy (p=0.35), 61.4 vs. 63.8Gy (p=0.1), and 59.5 vs. 60.9Gy (p=0.31), respectively. Similarly, mean rectum 0.1, 1, and 2cc doses for MVC vs. SVC were 67.2 vs. 75.4Gy (p=0.005), 60.0 vs. 65.6Gy (p=0.008), and 57.3 vs. 62.0Gy (p=0.015), respectively, and mean sigmoid doses were 56.3 vs. 60.5Gy (p=0.10), 50.9 vs. 53.1Gy (p=0.09), and 49.1 vs. 50.7Gy (p=0.10), respectively. The 3D CT-/MR-based plan with MVC may provide better dose distribution in the management of certain clinical situations of vaginal cancer requiring intracavitary brachytherapy, especially in minimizing potential late rectal complications.