Long-term intra-fractional motion of the prostate using hydrogel spacer during Cyberknife® treatment for prostate cancer – a case reportReport as inadecuate

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Radiation Oncology

, 9:186

Clinical Radiation Oncology


BackgroundThere is a trend towards hypofractionated stereotactic radiotherapy RT in prostate cancer to apply high single doses in a few fractions. Using the Cyberknife® robotic system multiple non-coplanar fields are usually given with a treatment time of one hour or more. We planned to evaluate organ motion in this setting injecting a hydrogel spacer to protect the anterior rectal wall during treatment.

MethodsA 66 years old man with low risk prostate cancer was planned for robotic hypofractionated stereotactic RT. After implantation of fiducial markers and a hydrogel spacer a total dose of 36.25 Gy in 5 fractions was given to the planning target volume clinical target volume + 3 mm. After each beam the corresponding data reporting on the intra-fractional movement were pre-processed, the generated log-files extracted and the data analysed according to different directions: left -right LR; anterior - posterior AP; inferior -superior IS. Clinical assessments were prospectively done before RT start, one week after the end of treatment as well as 1, 6 and 12 months afterwards. Symptoms were documented using Common Toxicity and Adverse Events Criteria 4.0.

ResultsTolerability of marker and hydrogel implantation was excellent. A total of 284 non-coplanar fields were used per fraction. The total treatment time for all fields per fraction lasted more than 60 minutes. The detected and corrected movements over all 5 fractions were in a range of +- 4 mm in all directions LR: mean 0,238 – SD 0,798; AP: mean 0,450 – SD 1,690; and IS: mean 0,908 – SD 1,518. V36Gy for the rectum was 0.062 ccm. After RT, grade 1-2 intestinal toxicity and grade 1 genitourinarytoxicity occurred, but resolved completely after 10 days. On 1-, 6- and 12-months follow-up the patient was free of any symptoms with only slight decrease of erectile function grade 1. There was a continuous PSA decline.

ConclusionsProstate movement was relatively low +- 4 mm even during fraction times of more than 60 minutes. The hydrogel spacer might serve as a kind of stabilisator for the prostate, but this should be analysed in a larger cohort of patients.

KeywordsProstate cancer Stereotactic radiotherapy Intra-fractional motion Hydrogel spacer Rectal toxicity AbbreviationsADTAndrogen deprivation therapy

APAnterior – posterior

CTVClinical target volume

FFBFFreedom from biochemical failure




ISInferior –superior

LRLeft – right

PTVPlanning target volume.

Electronic supplementary materialThe online version of this article doi:10.1186-1748-717X-9-186 contains supplementary material, which is available to authorized users.

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Author: Marcin Sumila - Andreas Mack - Uwe Schneider - Fabrizio Storelli - Jürgen Curschmann - Günther Gruber

Source: https://link.springer.com/

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