A Study of Transrectal Tumour Oxygen Measurements in Patients With Clinically Localized Prostate Cancer

Prostate cancer is now the most commonly diagnosed tumor among men in the United States. Most patients have tumors that are confined to the prostate gland at diagnosis and are suitable for treatment with surgery or radiotherapy (RT) that is aimed at curing the disease. Nevertheless, despite recent improvements in these treatments, a large number of men continue to die of prostate cancer. These patients often have spread of tumor to other areas of the body, and are treated with hormones that produce initial tumor shrinkage. However, over time the tumor learns to grow despite continued hormonal treatment. Effective therapy for patients with hormone-resistant prostate cancer is lacking and patients often deteriorate quickly and die. Thus, there is a need for better treatment that cures prostate cancer at an early stage, and a better understanding of the biology of prostate cancer specifically with respect to factors that determine the effectiveness of RT, the spread of tumor and the development of hormone-resistant disease.

Low levels of oxygen (hypoxia) are known to exist in many human tumors, and studies have shown that hypoxic tumors are less likely to be cured by RT. In addition, hypoxia may lead to lower cure rates following surgery, spread of cancer to other areas of the body, and changes in the genetic characteristics of the cancer cells that cause them to behave more aggressively.

The importance of hypoxia in prostate cancer has not previously been evaluated. The aims of this study are to determine how often hypoxia occurs in early prostate cancer and whether hypoxia influences the success of RT, tumor spread beyond the prostate to bones and other organs and the development of hormone-resistant disease. Patients will have tumor oxygen levels measured using a special fine-needle electrode system prior to beginning treatment with either RT or the combination of hormones plus RT. The measurements will be made through the rectum using ultrasound to position and guide the electrode. A biopsy of the tumor will be obtained at the site of the measurements, and this will be used to determine how oxygen influences changes in the genetic character of prostate cancer cells. A total of 195 patients will be evaluated in this way over 3 years.

This study will provide unique information about the behavior of prostate cancer, which may help explain why currently available treatments including surgery, RT and hormones fail to cure patients. Assuming that this study shows hypoxia to be important in prostate cancer, future work will focus on new anti-hypoxia treatments to be used in combination with surgery or RT with the aim of overcoming this obstacle and improving cure rates.