Why do we need more accurate intraprostatic localization of cancer?

Abstract

External beam radiotherapy is a key modality in the treatment of patients with prostate cancer. The goal of radiotherapy is to deliver a high radiation dose to tumourbearing tissues and minimize unnecessary irradiation of surrounding normal tissue structures. This maximizes the chance of tumour eradication and reduces the chance of normal tissue damage. In the treatment of prostate cancer the radiation dose that can be delivered to the prostate gland is often limited because of the potential risk of damage to the adjacent bladder, rectum and small bowel. Early results of clinical trials suggest that an increase in the delivered radiation dose is associated with improved prostate specific antigen (PSA) control [1] and it is hoped that this will translate into improved local control and overall survival in prostate cancer. Using intensity-modulated radiotherapy (IMRT), complex three-dimensional dose distributions can now be generated to concentrate very high radiation doses in areas of high tumour-cell density within the prostate gland, without significantly increasing the risk of normal tissue injury [2, 3]. IMRT may be used to escalate dose in excess of 80 Gy to the whole prostate gland, with a dose constraint on the anterior rectal wall [4]. To take full advantage of the opportunity of IMRT, imaging techniques that are able to map tumour volume within individual organs are needed [5, 6]. If it were possible to accurately determine the location of intraprostatic tumour nodules within the prostate gland, IMRT may allow dose escalation to these nodules with the aim of increasing tumour control with the benefit of lesser irradiation to surrounding structures [2]. It has been suggested that