Laboratory of Optoelectronics and Devices, Physics Department, Faculty of Sciences, UFAS1, Algeria , zchaoui@univ-setif.dz
Abstract: (357 Views)
Background: Based on recently published studies carried out in various institutions, the dosimetric evaluation was conducted to compare 5 and 7-field intensity-modulated radiation therapy (IMRT) plans. So far, dosimetric indexes have been used as the main parameters. The present study is new, it uses more sophisticated tools of evaluation based on radiobiologic indices as recommended. Materials and Methods: A comparative study of five and seven fields IMRT plans of sixteen randomly chosen prostate cancer cases has been evaluated radiobiologically. The modified Poisson model of Marsden allows us to calculate the tumor control probability (TCP) of the treated planning target volume (PTV60); The Lyman–Kutcher–Burman (LKB) model is used to calculate normal tissue complication probability (NTCP) of the organs at risk (rectal wall, bladder wall and femoral heads). We have elaborated an in-house program RADBIOFOR to calculate TCP and NTCP and use the dose volume histograms (DVH) from the treatment planning system (TPS) as input information. Results: A significant statistical difference was observed for the bladder (P-value=0.045). The statistical analysis for the rectum did not show a difference (P-value= 0.234). Meanwhile, 88% of the cases exhibited slightly lower toxicities with the 7-field compared to the 5-field. Conclusion: The present study recommends using a 7-field IMRT plan since it has proved to predict lower toxicities in the bladder and the rectum wall even though the 5-field predicts minor improvements in the local control in the tumor compared to the 7-field.
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