Comparison of dosimetric analysis of organs at risk and target volumes for ovoids and cylinders in endometrial carcinoma.

Purpose: To compare dose volume parameters of target and organs at risk in vaginal vault brachytherapy using ovoids or cylinder in post-operative endometrial carcinoma. Material and methods: The study was done among 25 histologically proven post-operative endometrial carcinoma patients requiring vaginal brachytherapy. All patients underwent both cylinder and ovoids application alternatively on weekly basis. Ovoids size ranged from 2 to 3 cm diameter. Diameters of cylinder ranged between 2.5 and 3.5 cm. Bladder, rectum, urethra, and clinical target volume (CTV) were contoured on CT simulation images. Prescribed dose was 6-7 Gy in 2-3 fractions at 0.5 cm from the surface of applicator. Results: The mean values of D90, D50, V150, V100, V90, and V50 of CTV were comparable between cylinder and ovoids plans. The mean dose of CTV was significantly higher with cylinder than with ovoids, and D100 was significantly higher with ovoids (mean = 15.63 Gy vs. 14.64 Gy, p = 0.016, and D100 = 37.82% vs. 42.86%, p = 0.042, for cylinder vs. ovoids). In the dosimetry of the vault, D90, D50, V100, V90, V50, and mean of the vault did not show any significant difference between cylinder and ovoids. The V150 was significantly higher with cylinder plans than ovoids, and D100 of the vault was significantly higher with ovoids plans (V150 = 14.81% vs. 6.86%, p = 0.02, and D100 = 37.77% vs. 44.80%, p = 0.029, for cylinder vs. ovoids). D0.1cc, D1cc, D2cc, and mean for the bladder, rectum, and urethra were comparable between the cylinder and ovoid plans. Conclusions: The present study showed that the dose to organs at risk, most of the dosimetric parameters of CTV, and vault were comparable between the cylinder and ovoid plans. Both applicators provide good reproducibility. The choice of applicator will ultimately depend on the institutional policies and oncologist decision. However, in patients with dog-ear configuration of the vagina, ovoids may be preferred as per ABS guidelines.

Prostate permanent implant brachytherapy with BARC I-125 Ocu-Prosta seeds.

AIM: The aim of this study is implementation and establishment of standard operating procedure for permanent prostate implant brachytherapy technique using BARC I-125 Ocu-Prosta seeds. MATERIALS AND METHODS: The transrectal ultrasound (US)-guided procedure was used for permanent implant procedure. The Best® Sonalis™ US Imaging System and Best NOMOS™ Treatment Planning system was used for volume study and implant procedure. The BARC provided I-125 Ocu-Pro radioactive seeds were implanted into the patient with help of Mick@ Applicator. The implant was performed based on pre-implant dosimetry and intraoperative planning performed during implant procedure. RESULTS: The necessary quality assurance tests were performed for US system before clinical use. The boost dose of 110 Gy was prescribed to the prostate volume of 34.71 cc. About 48 seeds with activity of 0.35 mCi (each) implanted into the prostate volume with reference to intraoperative planning. At the end of procedure, the patient underwent abdomen fluoroscopic examination, to ensure the seed counts in the prostate volume. The day after the implant, the patient was discharged. One month later a planning computed tomography and treatment planning was performed for seed position and dose verification. CONCLUSIONS: Low dose rate permanent implant brachytherapy has the advantage of being a one-time procedure and the existing long term follow-up supports its excellent outcome and low morbidity. BARC-BRIT is supplying the loose 125I seeds. These seeds can be easily implanted into the patient using Mick applicator. However, the pre-implant seed preparation and implant procedure may result some radiation exposure to staff involved. The radiation dose can be minimized with good practice. This report is one patient pilot study and intended to test the implant systems and standard operative procedure henceforth for permanent implant brachytherapy procedure.

Estimation of dose-volume parameters of female urethra as organ-at-risk during interstitial brachytherapy in gynecological malignancies.

PURPOSE: Interstitial brachytherapy (ISBT) is often used as post-external beam radiotherapy (EBRT) to treat locally advanced gynecological malignancies. Female urethra is in close proximity to the target during ISBT. However, it has not been evaluated as an organ-at-risk (OAR). Overlapping symptoms caused by radiation-induced bladder toxicity vs. urethral toxicity make it difficult to identify and report urethral toxicities separately. This was a retrospective study to estimate dose-volume parameters of female urethra during high-dose-rate ISBT. MATERIAL AND METHODS: Data of 24 patients with gynecological malignancies treated by ISBT were selected. Urethra and periurethral regions were retrospectively contoured. Mean volume, Dmax, Dmean, D2cc, D1cc, D0.5cc, D0.2cc, and D0.1cc were documented. Unpaired t-test was used for comparison of means. RESULTS: 20/24 Ca. cervix, 1/24 Ca. vagina, and 3/24 Ca. vaginal vault received 6-6.5 Gy in 4 ISBT fractions. Mean urethral length was 3.54 ±0.55 cm. Mean doses received by urethra per BT fraction were Dmax = 4.23 ±1.32 Gy, Dmean = 2.71 ±1.01 Gy, D0.2cc = 3.31 ±1.07, and D0.1cc = 3.54 ±1.09 Gy. Comparison of total BT 2 Gy equivalent dose (EQD2) with 4 fractions for urethra between patients with (9/24) and without anterior vaginal wall (15/24) involvement included Dmean = 18.79 ±7.49 Gy vs. 11.14 ±6.15 Gy*, D1cc = 10.90 ±10.03 Gy vs. 4.54 ±3.93 Gy*, D0.5cc = 19.50 ±8.69 Gy vs. 11.97 ±6.54 Gy*, D0.2cc = 23.78 ±8.94 Gy vs. 15.51 ±7.39 Gy*, and D0.1cc = 25.88 ±9.37 Gy vs. 17.39 ±8.03 Gy*, respectively (*p < 0.05). CONCLUSIONS: Female urethra receives significant doses during ISBT for gynecological malignancies, especially when the anterior vaginal wall is within the target volume. Reporting doses to urethra would enable to develop clinical correlation and dose-volume constraints for urethra as organ-at-risk in future.

Evaluation of dosimetric impact of inter-application and intra-application variations in fractionated high-dose-rate intra-cavitary brachytherapy of cervical cancer.

PURPOSE: To evaluate feasibility and safety of execution of optimized intra-cavitary brachytherapy (ICBT) plan of first fraction in subsequent fractions in high-volume, low-resource centers. MATERIAL AND METHODS: This non-randomized prospective study included 30 cervical cancer patients, who underwent 4 fractions of high-dose-rate (HDR)-ICBT in 2 applications, one week apart, 2 fractions per application delivered on two consecutive days. Computed tomography (CT) simulation was done before each fraction, organs at risk (OARs) were contoured on all sets of CT images. Optimized plans were generated for each set of CT images and executed for the treatment. Test treatment plans were retrospectively generated by applying first treatment fraction's dwell times adjusted for decay, and dwell positions of the applicator for subsequent treatment fractions paired t-test was performed to analyze D2cc dose variations of OARs among the paired sets of plans. RESULTS: Comparison between the plans showed daily plans provided lower D2cc to OARs than test plans. In intra-application plan comparison, there was a significant dose reduction to 2 cc sigmoid (p = 0.021) and bladder (p = 0.007) in daily plan. Mean D2cc of optimized and unoptimized plans were 361.35 ±114.01 and 411.70 ±152.73 for sigmoid, and 511.23 ±85.47 cGy and 553.57 ±111.23 cGy for bladder, respectively. In inter-application, D2cc rectum and sigmoid demonstrated a statistically significant dose variation (p = 0.002) and (p = 0.007), with mean D2cc rectum of optimized and unoptimized plans being 401.06 ±83.53 cGy and 452.46 ±123.97 cGy, and of 2 cc sigmoid 340.84 ±117.90 cGy and 387.79 ±141.36 cGy, respectively. CONCLUSIONS: Fractionated HDR brachytherapy amounts to significant variation in OAR doses if re-simulation and re-plan is not performed for every fraction and ICBT application. Therefore, plan of the day with optimization of the doses to target and OARs must be followed for each fraction.

Dosimetric comparison of various optimization techniques for high dose rate brachytherapy of interstitial cervix implants.

HDR brachytherapy treatment planning often involves optimization methods to calculate the dwell times and dwell positions of the radioactive source along specified afterloading catheters. The purpose of this study is to compare the dose distribution obtained with geometric optimization (GO) and volume optimization (VO) combined with isodose reshaping. This is a retrospective study of 10 cervix HDR interstitial brachytherapy implants planned using geometric optimization and treated with a dose of 6 Gy per fraction. Four treatment optimization plans were compared: geometric optimization (GO), volume optimization (VO), geometric optimization followed by isodose reshape (GO_IsoR), and volume optimization followed by isodose reshape (VO_IsoR). Dose volume histogram (DVH) was analyzed and the four plans were evaluated based on the dosimetric parameters: target coverage (V100), conformal index (COIN), homogeneity index (HI), dose nonuniformity ratio (DNR) and natural dose ratio (NDR). Good target coverage by the prescription dose was achieved with GO_ IsoR (mean V100 of 88.11%), with 150% and 200% of the target volume receiving 32.0% and 10.4% of prescription dose, respectively. Slightly lower target coverage was achieved with VO_IsoR plans (mean V100 of 86.11%) with a significant reduction in the tumor volume receiving high dose (mean V150 of 28.29% and mean V200 of 7.3%). Conformity and homogeneity were good with VO_ IsoR (mean COIN = 0.75 and mean HI = 0.58) as compared to the other optimization techniques. VO_IsoR plans are superior in sparing the normal structures while also providing better conformity and homogeneity to the target. Clinically acceptable plans can be obtained by isodose reshaping provided the isodose lines are dragged carefully.

A prospective randomized study comparing concurrent chemoradiation with weekly and 3 weekly cisplatin in locally advanced oropharyngeal carcinoma.

INTRODUCTION: The chemotherapy schedules with cytotoxic dose or weekly regimes are still challenging, weighing the benefits versus toxicities. This prospective randomized study is an attempt to assess the efficacy of two schedules of cisplatin in management of locally advanced HNSCC. OBJECTIVES: The objectives of this study was to evaluate tolerance, tumour response and toxicities of concurrent chemoradiation with cisplatin in weekly and three weekly regimes. METHODS: Locally advanced oropharyngeal squamous cell carcinoma patients fit for concurrent chemoradiation with cisplatin 40 mg/m2 (weekly) and 100 mg/m2 (3 weekly) were randomized to Arm A and B concurrently with radiotherapy of 70Gy/35frs/7 weeks. STATISTICAL ANALYSIS: Chi-square/ Fisher Exact test has been used to find the significance of study parameters on categorical scale between the groups. The statistical software SPSS 15.0 was used. RESULTS: Between December 2010 and January 2013, 60 patients were enrolled. The median cycles of cisplatin in Arm-A was 5 and 2 in Arm-B. The complete response of 80.9% vs 75% and partial response of 14.3% vs 12.5% was observed in both arms respectively. There was no statistical difference in acute radiation and hematological toxicities between the two groups. With median follow up of 28 months, the 2 and 5 years overall survival was 55% and 58%; 41.6% and 32.3% in arms A and B respectively. CONCLUSION: In our study of locally advanced oropharyngeal carcinoma treated with radical radiotherapy comparing concurrent chemotherapy with cisplatin weekly vs 3 weekly had no significant difference in overall response, complete response and acute toxicities.