Acute Toxicity in Hypofractionated/Stereotactic Prostate Radiotherapy of Elderly Patients: Use of the Image-guided Radio Therapy (IGRT) Clarity System

Abstract

Background: The use of intra-fractional monitoring and correction of prostate position with the Image Guided Radio Therapy (IGRT) system can increase the spatial accuracy of dose delivery. Clarity is a system used for intrafraction prostate-motion management, it provides a real-time visualization of prostate with a transperineal ultrasound. The aim of this study was to evaluate the use of Clarity-IGRT on proper intrafraction alignment and monitoring, its impact on Planning Tumor Volume margin and on urinary and rectal toxicity in elderly patients not eligible for surgery. Patients and Methods: Twenty-five elderly prostate cancer patients, median age=75 years (range=75-90 years) were treated with Volumetric Radiotherapy and Clarity-IGRT using 3 different schemes: A) 64.5/72 Gray (Gy) in 30 fractions on prostate and seminal vesicles (6 patients); B) 35 Gy in 5 fractions on prostate and seminal vesicles (12 patients); C): 35 Gy in 5 fractions on prostate (7 patients). Ultrasound identification of the overlapped structures to the detected ones during simulation has been used in each session. A specific software calculates direction and entity of necessary shift to obtain the perfect match. The average misalignment in the three-dimensional space has been determined and shown in a box-plot. Results: All patients completed treatment with mild-moderate toxicity. During treatment, genitourinary toxicity was 32% Grade 1; 4% Grade 2, rectal was 4% Grade 1. At follow-up of 3 months, genitourinary toxicity was 20% Grade 1; 4% Grade 2, rectal toxicity was 4% Grade 2. At follow-up of 6 months, genitourinary toxicity was 4% Grade 1; 4% Grade 2. Rectal toxicity was 4% Grade 2. Conclusion: Radiotherapy with the Clarity System allows a reduction of PTV margins, the amount of fractions can be reduced increasing the total dose, not exacerbating urinary and rectal toxicity with greater patient's compliance.In recent years, several clinical and experimental data have suggested an α/β ratio of 1.5 Gy for prostate cancer and this has encouraged the introduction of hypofractionation in its treatment (1). Prostate cancer α/β ratio seems lower than dose-limiting surrounding tissue of rectum and urinary bladder. The safe dose/fraction escalation improves the therapeutic ratio of prostate cancer radiotherapy, increasing cure rate with reducted toxicity. The α/β ratio for the rectum and bladder is generally assumed to be 3 Gy and 5-10 Gy, respectively. Moderate (dose 2.4-4 Gy) and extreme (dose 6.7-10 Gy) hypofractionation has been investigated in PC over the last decade (2-4). In many reviews and metaanalyzes, the ratio α/β is reported between 1.4 Gy and 1.93 Gy (1,(5)(6)(7)(8).

SBRT for Localized Prostate Cancer: CyberKnife vs. VMAT-FFF, a Dosimetric Study

“…In order to locate the tumor, in our case the prostate, and to check if its position changes during the treatment, some golden fiducials (usually four) are implanted in the prostate wall; the reconstruction of the prostate position by means of such markers allows adjustments of the accelerator real-time with respect to the target [ 17 , 18 , 19 ]. For the sake of completeness, in RT, when an accelerator is supported by an image system, the technology is called image guided radiotherapy (IGRT), and the use of accurate image guidance is crucial to minimize setup errors and facilitate the margins reduction between the gross tumor volume (GTV) and the Planning target volume (PTV), especially for SBRT.…”

Long-term Outcomes of Radiation Therapy for Prostate Cancer in Elderly Patients Aged ≥75 Years

“…Recently, it was reported that absorbable hydrogel spacers injected into the perirectal space could reduce adverse events not only in GI toxicities but also in GU toxicities and sexual function problems (34). It has also been suggested that the use of image-guided radiation therapy, which has been developed in recent years, may reduce toxicity in the treatment of elderly patients (35). Since such measures to reduce adverse effects are becoming available, there is no need to be reluctant to use RT because of the high incidence of Grade 2 adverse events.…”

Dosimetric evaluation study of IMRT and VMAT techniques for prostate cancer based on different multileaf collimator designs

“…These results were achieved employing agility VMAT and IMRT techniques, which were assisted by high-efficiency treatments that reduced treatment time even while delivering a high dose per fraction. It was reported that using modern radiotherapy technologies to reduce treatment duration resulted in greater compliance by patients and mild toxicity (Franco et al 2021). Also, using Agility MLC during treatment may enhance patient comfort and reduce intra-fraction motion around organs.…”