Some cancerous tumors continue to grow inside the prostate gland even after the patient has received radiation therapy for early prostate cancer. This growth can later lead to distant spread of cancer. Although current local salvage treatments may help some patients, they can also lead to many negative long-term side effects.
We do not fully understand where and how tumors continue to grow inside the prostate gland after radiation therapy. This kind of research is important so that we may improve the way we give radiation, and to determine which patients would benefit from more local treatments. More importantly, this research may one day allow us to specifically treat only the part of the prostate gland where the tumor is growing after radiation therapy. By focusing salvage therapy to the disease rather than the entire prostate gland, the side effects of treatment may be reduced.
Random biopsies of the prostate would only give us a small sample of that information. Magnetic resonance imaging (MRI) could in theory give a more complete picture of the tumor within the prostate gland. However, to understand the truth behind the images, we first need to compare the correct part of the image with the underlying prostate biopsy. This is difficult to do when biopsies and imaging are done at different times.
Researchers are starting to develop ways to do biopsies at the same time as MRI and to guide needles to specific locations within the prostate gland based on the MR images. To do this, patients must lie on their side or on their front for the entire procedure. In this study, we plan to improve this new biopsy technique and to apply it to patients who may have persistent prostate cancer after radiation therapy.
First, we plan to develop a special MRI table designed to allow needle placement inside the prostate gland while patients are lying on their backs. We then plan to show that the prostate gland is more stable in this position, which would improve the accuracy of needle placements, and to show that it is more comfortable for the patient. Ten healthy volunteers will be studied in the development phase of this research study. We then will determine the accuracy of needle placement first in a phantom and then in patients who may have persistent prostate cancer after radiation therapy.
In the second phase of the study, we will show that MRI-guided biopsies will lead to a better understanding of the truth behind the MR images. Specifically, we will compare biopsy results with the MRI to generate a three-dimensional tumor map of the prostate gland, to determine if there is a relationship between biopsy results and the MRI measurements, and to define the criteria for mapping persistent cancer inside the prostate gland after radiotherapy based solely on MRI measurements. Thirty patients who may have cancer growing in the prostate gland after radiotherapy will be enrolled on this study and will undergo MRI-guided prostate biopsies.
Finally, we plan to use the same approach to better understand oxygen levels in growing prostate tumors after radiation therapy. Tumors that have low oxygen levels tend to behave and respond differently to treatments. By measuring oxygen in tumors and comparing the results to MRI, we may be able to choose and adapt salvage treatments according to the level of oxygen in the tumor in different parts of the prostate gland.
Ultimately, this research will help and give hope to patients who have persistent prostate cancer after radiation therapy. This work is a necessary first step toward the development of minimally invasive image-guided salvage treatments that are focused on the growing tumor, while sparing the normal prostate gland and surrounding tissues, and reducing negative side effects. We fully expect to complete the proposed work and initiate therapeutic clinical trials testing the approach within 3 years.