PurposeThe aim of this study is to evaluate the decrease of biological equivalent dose and its correlation with local/loco-regional control of tumour in the treatment of cervical cancer when the strength of the Ir-192 high dose rate (HDR) brachytherapy (BT) source is reduced to single, double and triple half life in relation to original strength of 10 Ci (∼ 4.081 cGy x m2 x h−1).Material and methodsA retrospective study was carried out on 52 cervical cancer patients with stage II and III treated with fractionated HDR-BT following external beam radiation therapy (EBRT). International Commission on Radiation Units and Measurement (ICRU) points were defined according to ICRU Report 38, using two orthogonal radiograph images taken by Simulator (Simulix HQ). Biologically effective dose (BED) was calculated at point A for different Ir-192 source strength and its possible correlation with local/loco-regional tumour control was discussed.ResultThe increase of treatment time per fraction of dose due to the fall of dose rate especially in HDR-BT of cervical cancer results in reduction in BED of 2.59%, 7.02% and 13.68% with single, double and triple half life reduction of source strength, respectively. The probabilities of disease recurrence (local/loco-regional) within 26 months are expected as 0.12, 0.12, 0.16, 0.39 and 0.80 for source strength of 4.081, 2.041, 1.020, 0.510 and 0.347 cGy x m2 x h−1, respectively. The percentages of dose increase required to maintain the same BED with respect to initial BED were estimated as 1.71, 5.00, 11.00 and 15.86 for the dose rate of 24.7, 12.4, 6.2 and 4.2 Gy/hr at point A, respectively.ConclusionsThis retrospective study of cervical cancer patients treated with HDR-BT at different Ir-192 source strength shows reduction in disease free survival according to the increase in treatment time duration per fraction. The probable result could be associated with the decrease of biological equivalent dose to point A. Clinical end point of this study is more significant from double half life reduction of original source strength.
PurposeThe aim of this work was to evaluate the variation of dose in organs at risk (OARs) in fractionated high dose rate intracavitary brachytherapy (HDR-BT) for cervical cancer.Material and methodsA prospective study was carried out on 20 cervical cancer patients treated with fractionated (HDR-BT). International Commission on Radiation Units and Measurement (ICRU) bladder (bICRU) and rectum (rICRU) points were defined according to ICRU Report 38, using two orthogonal radiograph images taken by Simulator (Simulix HQ®) and prospectively kept to less than 80% of prescription dose to point A during real treatment planning process using the Plato Sunrise Treatment Planning System®.ResultsThe average variation of individuals in estimated doses of OARs in the inter fractional as well as in a single fraction were 2.4% and 0.7% of point A for rICRU, 4.3% and 1.6% for bICRU, and 0.8% & 0.2% for point B, whereas point A itself was found to be 1.6% & 0.6%.ConclusionsAverage variation of the delivery of dose per fraction was found well within the recommended limit. The study observed smaller variation of doses to OARs which could present better reproducibility of geometry of (HDR-BT) applicators and its relative displacement with critical structures. Transportation of patient from simulator room to treatment room causes small uncertainties in delivery dose.
BACKGROUNDCancer of any type is a serious and life-threatening illness, not uncommon in the general population. Cancer survivor can mean any person diagnosed with cancer from the time of initial diagnosis until his or her death. It includes people who are dying from untreatable cancer. Cancer survivor also includes those patients who are receiving or have received treatment with no active disease process and those who are not in the terminal stage of the illness. Cancer survivors tend to develop anxiety, depression and change in their quality of life as they have to make adjustment to many psychological and physical changes as well as financial constraint.
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