Influence of tumor size in the progression of venous tumor thrombus in renal cell carcinoma: A 7-year single-center experience.

Objective: The objective of the study is to describe the perioperative outcomes, disease-specific, and overall survival status in patients diagnosed with renal cell carcinoma with inferior vena cava (IVC) tumor thrombus. Patients and Methods: We did a retrospective analysis of all patients who underwent radical nephrectomy along with IVC thrombectomy from the year 2013 to 2020. Mayo's classification was used to stratify the level of IVC thrombus. Demographic, perioperative, histopathology data, complications, and survival status were analyzed. Results: Total number of patients included in the study was 39, (Male: Female = 84.6%: 15.4%). Median age of patients was 58 (interquartile range [IQR] 50-63) years. Median size of renal tumor (in cms) was 9.5 (IQR 7.5-12), 8 (IQR 7-11.5), 8.5 (IQR 7-11.75), and 11 (IQR 9.5-11) (P = 0.998) in level 1,2,3, and 4 tumors, respectively. Clear cell variant was seen in 32 patients (82%) with R0 resection in 17 patients. Twelve patients (30.7%) had systemic metastasis on presentation. The overall mean survival time was 66.4 months with 95% confidence interval (CI) (52.4-80.5 months). Mean recurrence-free survival is 76 months with (63-90) CI of 95%. Mean survival in patients who presented with metastasis is 47 months with 95% CI (52.4-80.5). Perioperative mortality rate was 5.12% in this study. Conclusion: The tumor size does not have an influence on the progression of tumor thrombus into IVC. Significant difference in survival was observed between different levels of thrombus with high mortality in level four tumors.

Volume changes during head-and-neck radiotherapy and its impact on the parotid dose - A single-institution observational study.

AIMS: This study aims at assessing the volume changes that occur in the targets (gross tumor volume and planning target volume [PTV]) and the organs at risk in squamous cell carcinoma of the head and neck during radiotherapy and assessing the dose changes that occur as a result of them. SETTINGS AND DESIGN: This was a prospective observational study in a tertiary care center after obtaining the appropriate scientific and ethics committee clearance. SUBJECTS AND METHODS: Forty-five patients diagnosed with squamous cell carcinoma of the head and neck, who were treated with intensity-modulated radiotherapy in the time period from March 2018 to May 2019, were enrolled in the study. A planning computed tomography (CT) scan (CTplan) was done for all patients, followed by scans after 15 fractions (CT15) and after 25 fractions (CT25). The volume changes and the subsequent dose changes were assessed and recorded. STATISTICAL ANALYSIS USED: Data entry was done in MS Excel spreadsheet. The continuous variables were expressed as mean + standard deviation. The comparison of normally distributed continuous variables was done by paired t-test. Data analysis was done by SPSS (Statistical Package for the Social Sciences) version 16.0. P < 0.05 was considered statistically significant. A multivariate linear regression model was constructed to study the correlation between mean dose to the parotid glands and the other variables. All statistical modeling and analysis were done using SAS (Statistical Analysis Software) version 9.4. RESULTS: Of the 45 patients, 25 were male and 20 were female. The majority of the patients had malignancies in the oral cavity (16) and hypopharynx (14). Most of them had Stage III/IV (AJCC v 8) disease (41). There were a 36% decrease in the PTV-high risk (PTV-HR) volume and a 6.05% decrease in the PTV-intermediate risk (PTV-IR) volume CT15. In CT25, the volume decrease in the PTV-HR and the PTV-IR was 47% and 9.06%, respectively. The parotid glands also underwent a reduction in their volume which has been quantified as 21.7% and 20.9% in the ipsilateral and contralateral parotids in CT15 and 36% and 33.6% in CT25, respectively. The D2 (dose received by 2% of the volume) and D98 (dose received by 98% of the volume) of the PTV-IR showed changes of +3.5% and -0.2% in CT15 and + 4.6% and -0.31% in CT25, respectively. The homogeneity index and conformity number of the PTV-IR changes by 0.03 and 0.08 in CT15 and by 0.04 and 0.12 in CT25, respectively. The mean dose to the ipsilateral parotid gland increased by 14% in CT15 and 19% in CT25. The mean dose to the contralateral parotid gland increased by 17% in CT15 and 25% in CT25. CONCLUSION: The dose to the parotid glands increases as a result of the changes that occur during the course of radiation. The changes are significant after 15 fractions of radiation. A replanning at this juncture might be considered to reduce the dose to the parotid glands.

Dosimetric Validation of Digital Megavolt Imager for Flattening Filter Free Beams in the Pre-Treatment Quality Assurance of Stereotactic Body Radiation Therapy for Liver Metastases.

AIM: The aim is to evaluate the use of digital megavolt imager (DMI) aS1200 in portal dosimetry with flattening filter free (FFF) beams. MATERIALS AND METHODS: Dosimetric properties of DMI is characterized at 6MV FFF beams for signal saturation, dose linearity, dependency on dose-rate and source-detector distance (SDD), signal lag (ghosting), and back scatter.  Portal dosimetry is done for twenty volumetric modulated arc therapy (VMAT) based stereotactic body radiotherapy (SBRT) plans for the treatment of liver metastases and the results are compared with repeated measurements of Octavius 4D. RESULTS: The detector signal to monitor unit (MU) ratio drops drastically below 25MU. The detector linearity with dose is within 1% and no evidence of signal saturation as such.  The aS1200 response variation across various dose rates and SDD is <0.4% and <0.2% respectively.  The effect of ghosting increased distinctly at higher dose rate but however it is negligible (0.1%).  The impact of back scatter is <0.3% because of additional shielding provided at the back of the detector.  The portal dosimetry results of SBRT QA plans evaluated at the gamma criteria of 2mm/2% (DTA/DD) both under global and local mode analysis has shown an average gamma passing rate of area gamma (<1) 97.9±0.8% and 96.4±0.9%.  The SBRT QA results observed in aS1200 are inline and consistent with Octavius 4D measured results. CONCLUSION: The characteristics of aS1200 evaluated at FFF beams have shown its potential ability as QA tool and can be used in SBRT QA for liver metastases with greater confidence.

Intrarectal fixative for positioning of the prostate for intensity modulated radiotherapy.

Dose escalation improves local control in carcinoma prostate, but rectal toxicity remains a concern. Various techniques have been there to reduce the dose to the rectum. Mobility of the prostate results in a necessary expansion of the target volume. We describe a new intrarectal fixative, developed in-house with transrectal ultrasonography through the fixative itself for localization of the organ by reporting a case with early carcinoma prostate. Concerns of rectal toxicity limit dose escalation in the treatment of prostate cancer. Intra- and interfraction prostate motion is a concern in dose conformity techniques. The intrarectal fixative system developed in-house physically separates the prostate and rectum during radiation treatment. Thus, both intra- and inter-fractional movement of the organ are addressed, therefore planning target volume expansion can be kept minimal.

A phantom study to determine the optimum size of a single collimator for shortening the treatment time in CyberKnife stereotactic radiosurgery of spherical targets.

Prolonged treatment execution time is a concern in CyberKnife robotic radiosurgery. Beam reduction and node reduction technique, and monitor unit optimization methods are adopted to reduce the treatment time. Usage of single collimator in the CyberKnife treatment plan can potentially reduce collimator exchange time. An optimal single collimator, which yields an acceptable dose distribution along with minimum number of nodes, beams, and monitor units, can be a versatile alternative for shortening treatment time. The aim of the present study is to find the optimal single collimator in CyberKnife treatment planning to shorten the treatment time with the acceptable dose distribution. A spherical planning target volume PTV1 was drawn in an anthropomorphic head and neck phantom. Plans with same treatment goals were generated for all the 12 collimators independently. D(95%) was selected as the prescribing isodose and the prescribed dose was 10 Gy. The plan of the optimal collimator size was evaluated for conformity, homogeneity, and dose spillage outside the target. The optimum collimator size and the target dimensions were correlated. The study was repeated with two other target volumes PTV2 and PTV3 for generalizing the results. Collimator sizes just above the diameter of the spherical PTVs were yielding least number of nodes and beams with acceptable dose distributions. The collimator size of 35 mm is optimum for the PTV1, whose diameter is 31.4 mm. Similarly, 50 mm collimator is optimum for PTV2 (diameter= 45.2 mm) and 20 mm collimator is optimum for PTV3 (Diameter = 17.3 mm). The total number of monitor units is found to reduce with increasing collimator size. Optimal single collimator is found to be useful for shortening the treatment time in spherical targets. Studies on two clinical targets, (a brain metastasis and a liver metastasis cases) show comparable results with the phantom study.