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Dosimetric Evaluation of Whole Pelvis Radiation Therapy of Prostate Cancer

H Mansoor*, E Osei, J Darko, Grand River Hospital, Kitchener, ON,CA.

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: The objective of this study was to conduct a comprehensive retrospective dosimetric analysis of whole pelvis radiation therapy plans for prostate cancer patients to aid in the development of an institutional criterion for volume-based whole pelvis radiation therapy treatment plans acceptability based on our current experiences and resources.


Methods: Retrospective dosimetric analysis was performed on the VMAT treatment plans for 179 prostate cancer patients treated over 3 years. Patients were either treated to a dose of 78Gy in 39 fractions with intact prostate, or 66Gy in 33 fractions for prostate bed. All patients had an initial treatment to the whole pelvis and a boost to the intact prostate or prostate bed. DVHs and dosimetric parameters for the PTV and organs at risk: rectum, bladder, femur heads were extracted from the Eclipse TPS.


Results: DVHs were quantitatively assessed in terms of dose coverage in the target volumes and dose to organs at risk (OARs) for each prescription cohort of patients. Further, dosimetric parameters were statistically analyzed at various dose levels: V40%, V50%, V65%, V66.6%, V70%, V75% and V80% for all the organs at risk.


Conclusion: The DVHs for the target volumes show a very narrow spread of distribution, however, a large spread was observed for the DVHs of the OARs. The mean DVHs derived from this study could be used to help optimise treatment planning and to reduce significant variation in treatment planning acceptability. This hopefully would help improve confidence in treatment planners or dosimetrists, reduce variation in treatment plans and enhance overall workflow while ultimately enabling efficient and optimal patient care.

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Keywords

Treatment Planning, Treatment Techniques, Tolerance Doses

Taxonomy

TH- External Beam- Photons: IMRT/VMAT dose optimization algorithms

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