Cone beam computed tomography-based online adaptive radiotherapy as a crucial step in increasing the effectiveness of cancer treatment — first clinical experience
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Abstract
Introduction. Online adaptive radiotherapy (oART) is an innovative approach that allows a treatment plan to be adjusted accurately and precisely on a daily basis according to changes in tumour and normal tissues during treatment courses.
Material and methods. The publication will focus on the presentation and subsequent stages of treatment planning, as well as their implementation, using the example of a patient with prostate cancer treated at our institution. The patient underwent hypofractionated radiotherapy with a daily fraction dose of 7.25 Gy to a total dose of 36.25 Gy.
Results. The median time required for the adaptation workflow (AT) was 29 min (SD 5 min). The mean bladder volume measured in the cone beam computed tomography (CBCT) images done before treatment was 184 cm³ and ranged from 146 cm³ to 203 cm³. For comparison, the blader volume at baseline computed tomography (CT) was 238 cm³. The mean rectal volume during treatment was 82 cm³ and ranged from 70cm³ to 100 cm³ and was also less than at baseline CT (122 cm³). The observed differences in patient geometry influenced changes in dose distribution in the planning target volume (PTV) and clinical target volume (CTV). In an extreme case (the fourth fraction of treatment), the patient treated according to the scheduled treatment plan would receive 99% (7.18 Gy) and 98% (7.11 Gy) of the prescribed dose only in 49% of CTV and 48% of PTV, respectively. The adaptation process improved dose distribution to cover 100% of the PTV and CTV to at least 98% and 99% respectively of the prescribed dose during each fraction of treatment.
Conclusions. The example shown presented very high interfractional mobility. The use of oART allowed for adjustment to those changes, ensuring proper coverage of the CTV and PTV with the therapeutic dose during each treatment fraction.
Keywords: online adaptive radiotherapyEthosprostate cancerradiosurgery
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