Using Ultrasound Spectrum Analysis (USA) to Guide Dose Escalated Prostate Brachytherapy

Overview

In standard treatment, the seeds are placed throughout the prostate to treat the entire prostate. This is done because it was impossible to know where the cancer was located within the prostate. A new technique has been developed using the same ultrasound imaging that you probably had when you had your biopsy. Using this technique, areas likely to contain prostate cancer can be identified.In this early study of 15 subjects, we will test if this method to plan your prostate seed implant is safe and can be done as part of regular care. Areas identified as suspicious for cancer will be treated with higher doses of radiation while those areas not demonstrating cancer will be treated to the standard minimum dose. The higher dose areas will receive two times the minimum dose the prostate usually receives. Because this technique is not perfect, those areas not identified as cancerous should be treated in case there is a cancer area that the technique did not identify. Subjects enrolled in this study will then be followed with this ultrasound technique over the next two years to monitor the changes to the cancerous areas and will undergo a biopsy two years after the procedure. Subjects will, of course, be monitored to assess the success of the technique and its side effects.

Prostate brachytherapy is an increasingly popular treatment for clinically localized prostate cancer.In properly selected patients, it is highly effective with biochemical (PSA) disease free survival rates of 80-87% at 5-10 years.However, the technique is currently limited by the inability to localize the cancer within the prostate. The multifocal nature of prostate cancer is well established. Because of the inability to know where within the prostate the cancer is located, radiation must be delivered throughout the gland. Although this blind approach leads to good results, it is clear that there are regions of the prostate and surrounding tissue that are overexposed to radiation while others are underexposed relative to their true need based on their tumor burden and their proximity to the tumor areas.Feleppa et al. at Riverside Research Institute (New York, NY), a non-profit ultrasound research center, have developed an ultrasound-based technique to identify cancer-containing areas within the prostate. This technique uses current ultrasound equipment already in use for prostate brachytherapy guidance. By extracting and processing the radiofrequency signal obtained from the ultrasound transducer in ways not done to create the standard B-mode ultrasound image, areas of cancer can be identified and displayed overlying the standard B-mode ultrasound image.In this study, we propose to obtain these ultrasound-based cancer-specific images of the prostate prior to the brachytherapy and use them to direct the dosimetry planning.The primary goal of this study is to demonstrate that this imaging modality can be incorporated into the treatment planning process for brachytherapy. Furthermore, we wish to demonstrate the improved dosimetry of the cancer-identified regions while maintaining the urethral dose guidelines noted above. We also wish to compare the differences in dose to the other adjacent normal structures (anterior rectum and right and left neurovascular bundles). Additionally, we seek to demonstrate, at a minimum, no increased toxicity with this approach and similar disease control rates. Of course, ultimately the goal will be to demonstrate a superior therapeutic ratio with this technique.