Indiana University School of Medicine, Indianapolis, IN

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PO-GePV-T-280 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: Most modern LINAC are installed with variety of photon energies from 6 MV to 18 MV. The conventional wisdom in external radiotherapy has been that higher energies are preferred for deep seated pelvic/abdominal lesions. With the introduction of IMRT/VMAT, the utility of higher photon energies for prostate cancer has been questioned. The aim of this systematic review was to analyze articles that performed dosimetric comparative study using different photon energies for prostate cancer radiotherapy.

Methods: An extensive literature was performed on PubMed database and Cochrane library using the following search terms: prostate, photon energy, radiotherapy, radiation therapy, intensity modulated radiation therapy, VMAT and RapidArc. Studies were included if at least two photon energies, plan quality (defined target coverage, conformity index and homogeneity index) and DVH of organ at risk (OAR- rectum, bladder, sigmoid, and femur) were reported. The following OAR dosimetric parameters were evaluated: V70 for the rectum and bladder, D50 for the femur and Dmax for Sigmoid

Results: 138 papers published in English journals fulfilled the initial search criteria. Of these, 13 studies fulfilled the eligibility criteria. In these 13 studies, 7, 4, 4 compare 6MV/10MV, 6MV/15MV, 6MV/18MV respectively. 9 reported OAR dosimetric data, 9 report treatment efficiency data (delivery time and MU). The 14 studies comprised a total of 248 patients and a total of 700 treatment plans (382 VMAT plans and 318 IMRT Plans) for the different photon energies were generated.

Conclusion: There was no significant difference in treatment plan quality as defined by target coverage, conformity index and homogeneity index amongst the different photon energies. The average number of MUs delivered per prescribed gray decreased as photon energy increased. The normal tissue integral dose decreased with increase in photon energy. The effect on photon energy on the OAR did not have a clear pattern.

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