Optimization in high dose rate vaginal cylinder for vaginal cuff irradiation

SummaryAimThe aim of this study is to evaluate the influence of high dose rate (HDR) brach-ytherapy source step size, source dwell position, dose prescription depth, dose specification points and optimization technique on dose distribution around Microselectron HDR brachytherapy vaginal cylinders and to evaluate the influence of distal dwell position and optimization technique on rectal and bladder dose of patients treated for vaginal cuff irradiation.Materials/MethodsOrthogonal radiographs of vaginal cylinders of diameter 2.0, 2.5, 3.0 and 3.5cm form the basis of the study. Dose distribution using the PLATO brachytherapy treatment planning system (version 14.1) was generated. Two different HDR cylinder models, namely the non-curved dome model (NCDM) and curved dome model (CDM), were studied. To evaluate bladder and rectum dose in the patients NCDM was used.ResultsCDM gives more uniform dose distribution around the cylinder than NCDM. Dose prescription at 5mm depth from the surface results in very high dose to apex and dome as compared with the surface dose prescription. Dose prescription depth and dwell positions influence the length of prescription isodose. Optimization method and dwell positions affect the bladder and rectal dose of the studied patients.ConclusionsUniform dose distribution can be obtained for HDR vaginal cylinders by appropriately selecting dose specification points and optimization method. Dose distribution can be configured to provide a uniform dose on the surface, if the apex and curved surface of the cylinder are considered for dose specification and optimization. Appropriate HDR parameters are identified to minimize the dose to the apex of the vaginal cylinder, essential to reduce the dose to overlying small bowel and reduce the dose to rectum and bladder

Optimization in high dose rate vaginal cylinder for vaginal cuff irradiation

AimThe aim of this study is to evaluate the influence of high dose rate (HDR) brach-ytherapy source step size, source dwell position, dose prescription depth, dose specification points and optimization technique on dose distribution around Microselectron HDR brachytherapy vaginal cylinders and to evaluate the influence of distal dwell position and optimization technique on rectal and bladder dose of patients treated for vaginal cuff irradiation.Materials/MethodsOrthogonal radiographs of vaginal cylinders of diameter 2.0, 2.5, 3.0 and 3.5cm form the basis of the study. Dose distribution using the PLATO brachytherapy treatment planning system (version 14.1) was generated. Two different HDR cylinder models, namely the non-curved dome model (NCDM) and curved dome model (CDM), were studied. To evaluate bladder and rectum dose in the patients NCDM was used.ResultsCDM gives more uniform dose distribution around the cylinder than NCDM. Dose prescription at 5mm depth from the surface results in very high dose to apex and dome as compared with the surface dose prescription. Dose prescription depth and dwell positions influence the length of prescription isodose. Optimization method and dwell positions affect the bladder and rectal dose of the studied patients.ConclusionsUniform dose distribution can be obtained for HDR vaginal cylinders by appropriately selecting dose specification points and optimization method. Dose distribution can be configured to provide a uniform dose on the surface, if the apex and curved surface of the cylinder are considered for dose specification and optimization. Appropriate HDR parameters are identified to minimize the dose to the apex of the vaginal cylinder, essential to reduce the dose to overlying small bowel and reduce the dose to rectum and bladder

Quality assurance of simultaneous treatment of two targets in pelvic region planned with single isocenter using three dimensional conformal radiotherapy (3DCRT) technique

Purpose: The purpose of this study was to conduct quality assurance of a three dimensional conformal radiotherapy (3DCRT) of two targets in pelvis region planned with single isocenter technique. Methods: A treatment plan was generated with two identical water phantoms with ionization chamber (IC) sleeves (IC-1 & IC-2), simulated as if targets are in pelvis region, simultaneously irradiated with single isocenter technique with a dose prescription of 300 cGy for point dose verification. A two dimensional ion chamber array detector was used for fluence verification.Results: Calculated minimum, mean and maximum dose (in cGy) for IC-1 & IC-2 were 295, 303 and 307 as per dose volume histogram. The global dose maximum was found to be 307.4 cGy. Measured point doses to both lesions were within ±2.5% of the computed dose. A pass percentage of 97% was obtained with the set of criteria 3 mm distance to agreement and 3% dose difference for fluence verification.Conclusion: Treatment execution of two targets simultaneously with single isocenter can reduce positional errors and delivery time

Quality assurance of simultaneous treatment of two targets in pelvic region planned with single isocenter using three dimensional conformal radiotherapy (3DCRT) technique

Purpose: The purpose of this study was to conduct quality assurance of a three dimensional conformal radiotherapy (3DCRT) of two targets in pelvis region planned with single isocenter technique. Methods: A treatment plan was generated with two identical water phantoms with ionization chamber (IC) sleeves (IC-1 &amp; IC-2), simulated as if targets are in pelvis region, simultaneously irradiated with single isocenter technique with a dose prescription of 300 cGy for point dose verification. A two dimensional ion chamber array detector was used for fluence verification.Results: Calculated minimum, mean and maximum dose (in cGy) for IC-1 &amp; IC-2 were 295, 303 and 307 as per dose volume histogram. The global dose maximum was found to be 307.4 cGy. Measured point doses to both lesions were within ±2.5% of the computed dose. A pass percentage of 97% was obtained with the set of criteria 3 mm distance to agreement and 3% dose difference for fluence verification.Conclusion: Treatment execution of two targets simultaneously with single isocenter can reduce positional errors and delivery time.</p

Genetic Variants in CD44 and MAT1A Confer Susceptibility to Acute Skin Reaction in Breast Cancer Patients Undergoing Radiation Therapy

Purpose: Heterogeneity in radiation therapy (RT)-induced normal tissue toxicity is observed in 10% of cancer patients, limiting the therapeutic outcomes. In addition to treatment-related factors, normal tissue adverse reactions also manifest from genetic alterations in distinct pathways majorly involving DNA damage-repair genes, inflammatory cytokine genes, cell cycle regulation, and antioxidant response. Therefore, the common sequence variants in these radioresponsive genes might modify the severity of normal tissue toxicity, and the identification of the same could have clinical relevance as a predictive biomarker.Methods and Materials: The present study was conducted in a cohort of patients with breast cancer to evaluate the possible associations between genetic variants in radioresponsive genes described previously and the risk of developing RT-induced acute skin adverse reactions. We tested 22 genetic variants reported in 18 genes (ie, NFE2L2, OGG1, NEIL3, RAD17, PTTG1, REV3L, ALAD, CD44, RAD9A, TGFbR3, MAD2L2, MAP3K7, MAT1A, RPS6KB2, ZNF830, SH3GL1, BAX, and XRCC1) using TaqMan assay-based real-time polymerase chain reaction. At the end of RT, the severity of skin damage was scored, and the subjects were dichotomized as nonoverresponders (Radiation Therapy Oncology Group grade 2) for analysis.Results: Of the 22 single nucleotide polymorphisms studied, the rs8193 polymorphism lying in the micro-RNA binding site of 30-UTR of CD44 was significantly (PZ.0270) associated with RT-induced adverse skin reactions. Generalized multifactor dimensionality reduction analysis showed significant (PZ.0107) gene-gene interactions between MAT1A and CD44. Furthermore, an increase in the total number of risk alleles was associated with increasing occurrence of overresponses (PZ.0302).Conclusions: The genetic polymorphisms in radioresponsive genes act as geneticmodifiers of acute normal tissue toxicity outcomes after RT by acting individually(rs8193), by gene-gene interactions (MAT1A and CD44), and/or by the additive effects of risk alleles

Demographic and clinical details of head and neck cancer patients.

<p>Demographic and clinical details of head and neck cancer patients.</p

Multivariate analysis for CAT and NBN polymorphisms with radiation-induced oral mucositis in presence of alcohol among head and neck cancer patients.

<p>Multivariate analysis for CAT and NBN polymorphisms with radiation-induced oral mucositis in presence of alcohol among head and neck cancer patients.</p

Polymorphisms in Radio-Responsive Genes and Its Association with Acute Toxicity among Head and Neck Cancer Patients

<div><p>Cellular and molecular approaches are being explored to find a biomarker which can predict the development of radiation induced acute toxicity prior to radiation therapy. SNPs in radiation responsive genes may be considered as an approach to develop tools for finding the inherited basis of clinical radiosensitivity. The current study attempts to screen single nucleotide polymorphisms/deletions in DNA damage response, DNA repair, profibrotic cytokine as well as antioxidant response genes and its predictive potential with the normal tissue adverse reactions from 183 head and neck cancer patients undergoing platinum based chemoradiotherapy or radiotherapy alone. We analysed 22 polymorphisms in 17 genes having functional relevance to radiation response. Radiation therapy induced oral mucositis and skin erythema was considered as end point for clinical radiosensitivity. Direct correlation of heterozygous and mutant alleles with acute reactions as well as haplotype correlation revealed NBN variants to be of predictive significance in analysing oral mucositis prior to radiotherapy. In addition, genetic linkage disequilibrium existed in XRCC1 polymorphisms for >grade 2 oral mucositis and skin reaction indicating the complex inheritance pattern. The current study indicates an association for polymorphism in NBN with normal tissue radiosensitivity and further warrants the replication of such studies in a large set of samples.</p></div