Improvement in toxicity in high risk prostate cancer patients treated with image-guided intensity-modulated radiotherapy compared to 3D conformal radiotherapy without daily image guidance

Svend Aage Engelholm,Jung Hun Oh,Peter Meidahl Petersen,Joen Sveistrup,Tobias Pommer,Joseph O Deasy,Per Munck af Rosenschöld

doi:10.1186/1748-717x-9-44

Abstract

BackgroundImage-guided radiotherapy (IGRT) facilitates the delivery of a very precise radiation dose. In this study we compare the toxicity and biochemical progression-free survival between patients treated with daily image-guided intensity-modulated radiotherapy (IG-IMRT) and 3D conformal radiotherapy (3DCRT) without daily image guidance for high risk prostate cancer (PCa).MethodsA total of 503 high risk PCa patients treated with radiotherapy (RT) and endocrine treatment between 2000 and 2010 were retrospectively reviewed. 115 patients were treated with 3DCRT, and 388 patients were treated with IG-IMRT. 3DCRT patients were treated to 76 Gy and without daily image guidance and with 1–2 cm PTV margins. IG-IMRT patients were treated to 78 Gy based on daily image guidance of fiducial markers, and the PTV margins were 5–7 mm. Furthermore, the dose-volume constraints to both the rectum and bladder were changed with the introduction of IG-IMRT.ResultsThe 2-year actuarial likelihood of developing grade > = 2 GI toxicity following RT was 57.3% in 3DCRT patients and 5.8% in IG-IMRT patients (p < 0.001). For GU toxicity the numbers were 41.8% and 29.7%, respectively (p = 0.011). On multivariate analysis, 3DCRT was associated with a significantly increased risk of developing grade > = 2 GI toxicity compared to IG-IMRT (p < 0.001, HR = 11.59 [CI: 6.67-20.14]). 3DCRT was also associated with an increased risk of developing GU toxicity compared to IG-IMRT.The 3-year actuarial biochemical progression-free survival probability was 86.0% for 3DCRT and 90.3% for IG-IMRT (p = 0.386). On multivariate analysis there was no difference in biochemical progression-free survival between 3DCRT and IG-IMRT.ConclusionThe difference in toxicity can be attributed to the combination of the IMRT technique with reduced dose to organs-at-risk, daily image guidance and margin reduction.

Highlights

Image-guided radiotherapy (IGRT) facilitates the delivery of a very precise radiation dose
For the T-stage the results indicate the hazard ratio for patients with T-stage ≥ T2c compared to patients with T-stage ≤ T2b
We found that 3D conformal radiotherapy (3DCRT) patients experienced significantly more toxicity than imageguided intensity-modulated radiotherapy (IG-intensity modulated radiotherapy (IMRT)) patients

Summary

Introduction

Image-guided radiotherapy (IGRT) facilitates the delivery of a very precise radiation dose. In this study we compare the toxicity and biochemical progression-free survival between patients treated with daily imageguided intensity-modulated radiotherapy (IG-IMRT) and 3D conformal radiotherapy (3DCRT) without daily image guidance for high risk prostate cancer (PCa). The concept of image guided radiotherapy (IGRT) has been introduced in the treatment of PCa. IGRT is often based on the implantation of fiducial gold markers in the prostate. With markers implanted in the prostate, the position of the prostate can be verified before each treatment fraction using portal imaging This limits the interfractional variability in the position of the prostate and as a consequence the PTV margins can be reduced [3]. A reduction in PTV margins should reduce the dose to the organs at risk and result in less toxicity [4]. There is concern that large margin reductions might increase the risk of geographical miss of the target, which might result in higher rates of local failure [5]

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