Prostate cancer is the most common cancer in men and increasing numbers of patients are undergoing external beam radiotherapy and brachytherapy (seed implants) to treat their disease. However, follow-up of these patients is hampered by the difficulty of interpreting conventional measurements after radiation treatment (such as prostate specific antigen (PSA) levels, biopsy results, and clinical examination). Currently, magnetic resonance (MR) imaging is the best method of pretreatment staging, but it is still underdeveloped and has not been used to examine patients after radiation therapy. Innovative procedures are required to improve the quality of existing techniques.
Recent research has indicated that two new quantitative MR methods, relaxation time (T2) mapping and the analysis of contrast agent kinetics, may provide a better means of identifying cancer in the prostate gland. These techniques will be tested in a group of 21 patients previously selected to undergo radiation therapy. One MR exam will be carried out before the start of radiation therapy, and a further exam will be obtained 12 months after therapy. The results of these exams will be compared with clinical findings, biopsy data, and PSA measurements collected every 3 months during the course of the study. It is anticipated that changes in the MR data after treatment will correspond to changes seen in PSA levels and biopsy findings, but the images will be used to identify the precise location of these changes. Furthermore, the MR data will be used to assess the degree of blood vessel development (angiogenesis) associated with tumor growth. In this way, it may be possible to use the MR techniques to help direct more aggressive treatment to those patients with a poor prognosis. This type of data is normally available only through invasive transurethral resection and pathologic specimen analysis.
The combination of approaches is novel and provides an important step forward in the quantitative understanding of MR studies of the prostate gland. We expect that this innovative study will demonstrate the importance of quantitative MR techniques for measuring the effect of radiation therapy on the prostate. Furthermore, it will directly impact therapeutic decisions and lead to further studies with the aim of reducing the number of deaths associated with prostate cancer.