Bony-based and prostate-based image guidance for lo-calized prostate cancer radiotherapy

Saulo Santos Fortes,Luiz Antonio Ribeiro Da Rosa

doi:10.15392/bjrs.v8i1.1175

Saulo Santos Fortes, Luiz Antonio Ribeiro Da Rosa

Open Access

https://doi.org/10.15392/bjrs.v8i1.1175

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Abstract

An important modality for the treatment of prostate cancer is teletherapy. The use of image-guided radiotherapy (IGRT) is a valuable tool in this treatment. This study retrospectively compared how repositioning the patient based on bone structure (B-ISO) and the prostate itself (P-ISO) affected the volumetric dose in the rectum, bladder, and clinical treatment volume (CTV). Additionally, the probability of normal tissue complication (NTCP) for the rectum was computed. We evaluated 155 cone-beam computed tomography (CBCT) from 8 patients. The treatment plans used beam modulation techniques. The planning target volume (PTV) margin adopted in both scenarios was 1 cm. The organs of interest were outlined over each CBCT and then treatment plans were applied so that the absorbed dose could be computed. NTCP values were calculated for the rectum. Analyzing dose-volume metrics published by the Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC), there was no significant difference between the two repositioning strategies for the rectum and bladder. There was a slight degradation in CTV coverage for the B-ISO strategy, but still with adequate coverage. Analysis of the uniform equivalent dose (EUD) and NTCP for the rectum showed little sensitivity to the strategy used. The present study showed that the use of CBCT in radiotherapy for prostate cancer treatment did not significantly improve volumetric doses for the rectum, bladder, and CTV, as well as NTCP for the rectum.

Highlights

Prostate cancer is estimated to be the most common in men in Brazil, excluding non-melanoma skin cancer [1]
Many researchers [5, 6] have shown that intensity-modulated radiotherapy (IMRT) reduces treatment side effects and improves survival rates when compared to the 3D conformal radiotherapy technique (3DCRT)
Degradation of dose distributed at clinical target volume (CTV) was observed for the group in which the B-ISO strategy was used for the V100%, V95%, and D99% metrics

Summary

Introduction

Prostate cancer is estimated to be the most common in men in Brazil, excluding non-melanoma skin cancer [1]. Teletherapy is an important treatment modality for localized prostate cancer. The radiotherapy technique for prostate irradiation has changed significantly over the years [2]. The use of beam intensity-modulated radiotherapy (IMRT), a technique capable of distributing high doses of radiation to the target volume with a highly conformal dose distribution, allowed the scaling of the prescribed prostate dose [3]. Many researchers [5, 6] have shown that IMRT reduces treatment side effects and improves survival rates when compared to the 3D conformal radiotherapy technique (3DCRT). Additional caution is required when distributing high doses of radiation to the prostate, as it may vary its position and shape during both intrafraction and interfraction treatment [6]

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Discussion

Conclusion