K. Ramalingam

CAG repeat length polymorphism in the androgen receptor gene and breast cancer risk: data on Indian women and survey from the world

We analyzed the length of the CAG repeats of the androgen receptor gene in Indian women with breast cancer, and compared the data with that of other populations across the world in an attempt to find a potential pattern of association. The study was undertaken on 1,408 individuals comprising 747 breast cancer patients and 661 control individuals recruited from three southern states of India: Andhra Pradesh, Tamil Nadu, and Karnataka. The comparison revealed no difference in mean length of the repeat between cases and controls in any of the three groups or in the analysis of pooled data. No significant difference between pre- and post-menopausal cases in any of the three groups or in the analysis of pooled data was observed. Most of the studies to date support either positive association (longer repeats—increased disease risk) or no association, and only 2 out of 20 studies reported negative association (inverse correlation between repeat length and disease risk). Comparison of these data with those from other populations revealed several interesting facts. Particularly notable is that repeat length shows association with breast cancer risk in a population-specific manner with most of the studies on American and Canadian women showing positive association, whereas those on Australian and Israeli women showing no association. Only one study had been conducted on other populations including Asians/South Asians; this restricted us from finding any patterns of association in these populations.

A mitochondrial DNA variant 10398G>A in breast cancer among South Indians: An original study with meta-analysis

The m.10398G>A polymorphism in the MT-ND3 gene has been linked to the manifestation of several neurodegenerative disorders and cancers. Several research groups have analyzed the association between m.10398G>A polymorphism and breast cancer; however, the results do not follow a consensus. We have studied this polymorphism in three Dravidian populations from South India. Analysis on 716 cases and 724 controls found no association between m.10398G>A polymorphism and breast cancer [OR = 0.916 (0.743-1.128); P = 0.409]. Menopausal stratification also revealed no significant association in either pre-menopausal or post-menopausal breast cancer groups. In addition, we undertook a meta-analysis on 16 study groups, comprising a total of 7202 cases and 7490 controls. The pooled odds ratio suggested no significant association of m.10398G>A substitution with breast cancer [OR = 1.016 (0.85-1.22); P = 0.86]. In conclusion, there is no evidence of association between m.10398G>A polymorphism and breast cancer risk among South Indian women. Meta-analysis suggested no overall correlation between this polymorphism and breast cancer risk.

SU‐E‐T‐766: Verification of Volumetric Modulated Arc Therapy Plans with Independent Three Dimensional Dose Computation Algorithm

Purpose: To verify the volumetric modulated arc therapy (Rapidarc) plans using a independent three dimensional dose computation algorithm using COMPASS system. Methods: Rapidarc is a treatment technique which produces conformal dose distribution by delivering the dose in a rotational fashion while simultaneously changing MLC position, dose rate as well as gantry speed. COMPASS dosimetry system uses the Collapsed Cone Convolution(CCC) algorithm as a dose calculation engine which requires machine model information and beam modeling to display the 3D dose distribution on a patient CT data. Treatment plans (10 patients) generated for Rapidarc on Eclipse (version 8.9) Treatment Planning System (TPS) using Analytical Anisotropic Algorithm (AAA) were exported as DICOM file to COMPASS for recalculation using CCC algorithm. Pilot studies were performed for 2DRT, 3DCRT and IMRT plans prior to VMAT plan verification. The doses and dose‐volume histograms computed using CCC were compared with TPS calculated plans. Plans were analyzed in terms of Conformity Index (CI) for PTV, maximum and mean doses for OARs and difference in three dimensional gamma. Results: The average 3D mean gamma for 1mm(DTA) and 1%(DD) criteria for 2DRT and 3DCRT was 0.11 ±0.002 . Maximum and minimum deviation of PTV Volume receiving 95% of the prescribed dose(V95%) for IMRT and Rapidarc were found to be 1.01%, 0.79% and 1.24%, 0.86% respectively. Average deviation of maximum and mean doses of OARs for IMRT and Rapidarc were 0.91±0.002 %, 0.55±0.008 % and 0.25±0.005 %, 1.05±0.009 % respectively. Conclusions: This study illustrates that the compass three dimensional dosimetry system can be used as an accurate and effective tool to clinically validate the Rapidarc plans independently.

SU‐E‐T‐188: Patient Specific Quality Assurance for Volumetric Modulated Arc Therapy (RapidArc) Using COMPASS 3D Dosimetry System

Purpose: To implement the COMPASS (IBA, Inc) quality assurance (QA) system as a patient specific QA tool for Volumetric Modulated Arc Therapy. Methods: RapidArc is a treatment technique which produces conformal dose distribution by delivering the dose in a rotational fashion while simultaneously changing MLC position, dose rate as well as gantry speed. The COMPASS has the potential to calculate and display the delivered 3D dose distribution on a patient CT data by using beam modeling, dose map from detector measurements (I‐MatriXX Evolution) and dose map reconstruction using Collapsed Cone Convolution Algorithm. Dose maps for 10 Ten RapidArc plans were measured using I‐MatriXX Evolution with a gantry mount (SSD=76.2cm) along with gantry angle sensor. This device captures the RapidArc plan delivery in real‐time in a pre‐treatment QA context. The measurement data were read directly by the control software, which provides the ability to import patient plan data from the treatment planning system via DICOM export. The COMPASS software also provides the user a dose calculation engine, including a physics based head fluence model. The doses and dose‐volume histograms reconstructed from the fluence measurements were compared to the TPS calculated plans.Results: Maximum and minimum deviation of PTV Volume receiving 95% of the prescribed dose(V95%) was found to be −2.89% and 0.16% respectively and mean deviation −1.12%. Average deviation of maximum and mean doses of OARs (organ at risk) were −0.5880±0.012% and − 0.6952±0.011% respectively. Average 3D mean gamma for 3mm and 3% criteria was found to be 0.067±0.0013 and Maximum absolute dose deviation at isocentre was 1.3573% Conclusions: Compass system can be used as an accurate and visually enhanced patient specific QA tool for VMAT plans to provide a complete clinical relevance of dose discrepancies for better patient treatment.