Abstract
PurposeThe aim of the study was to estimate interfractional deviations in patient and prostate position, the impact of the frequency of online verification on the treatment margins, and to assess acute radiation reactions of high-dose external beam image-guided intensity-modulated radiotherapy (IG-IMRT) of localized prostate cancer.Patients and methodsIG-IMRT was performed by daily online verification of implanted fiducial prostate markers using a megavoltage electronic portal imaging device (EPID). A total of 1011 image-guided treatment fractions from 23 consecutive unselected prostate cancer patients were analyzed. The median total dose was 79.2 Gy (range 77.4–81.0 Gy). Acute radiation reactions were assessed weekly during radiotherapy using the Common Terminology Criteria for Adverse Events (CTCAE) v.4.03.ResultsA relevant combined patient set-up and prostate motion population random error of 4–5 mm was observed. Compared to daily IGRT, image guidance every other day required an expansion of the CTV–PTV (clinical target volume–planning target volume) margin of 8.1, 6.6, and 4.1 mm in the longitudinal, vertical, and lateral directions, thereby, increasing the PTV by approximately 30–40 %. No grade 3 or 4 acute radiation reactions were observed with daily IG-IMRT.ConclusionA high dose with surprisingly low acute toxicity can be applied with daily IG-IMRT using implanted fiducial prostate markers. Daily image guidance is clearly superior to image guidance every other fraction concerning adequate target coverage with minimal margins.
Highlights
Zusammenfassung Ziel Ziel der Studie war es, die interfraktionelle Variabilität der Patientenlagerung und Prostataposition, den Einfluss der Bildgebungsfrequenz und die akuten Strahlenreaktionen bei einer hochdosierten bildgesteuerten intensitätsmodulierten Strahlentherapie (IG-intensity-modulated radiotherapy (IMRT)) des Prostatakarzinoms zu untersuchen
Image guidance every other fraction compared to no image guidance substantially reduced the combined error
Considerable error remains after image guidance every other fraction
Summary
Zusammenfassung Ziel Ziel der Studie war es, die interfraktionelle Variabilität der Patientenlagerung und Prostataposition, den Einfluss der Bildgebungsfrequenz und die akuten Strahlenreaktionen bei einer hochdosierten bildgesteuerten intensitätsmodulierten Strahlentherapie (IG-IMRT) des Prostatakarzinoms zu untersuchen. Bildgesteuerte Strahlentherapie (IGRT) würde bei jeder zweiten Bestrahlungsfraktion im Vergleich zu täglicher IGRT eine Erweiterung des CTV(klinisches Zielvolumen)-PTV(Planungszielvolumen)Sicherheitssaums von 8,1 mm, 6,6 mm und 4,1 mm in der longitudinalen, vertikalen und lateralen Ebene erfordern. Studies revealed a relevant prostate motion variability [20], evaluated the patient set-up variability without image guidance [15], and estimated the treatment margins for the combined error of both factors [17]. Image-guided radiotherapy (IGRT) and reverse planned intensity-modulated radiotherapy (IMRT) are current radiation techniques commonly used to minimize the high-dose region without compromising tumor coverage for the definitive radiotherapy of localized prostate cancer. The goal of the study was to assess prostate motion variability and patient set-up variability, and to estimate the safety margin to accommodate for the combined error of both factors. Acute radiation reactions were assessed weekly during radiotherapy to evaluate the tolerance to high radiation doses applied using daily IG-IMRT
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