Prostate tissue stiffness as measured with a resonance sensor system: a study on silicone and human prostate tissue in vitro

Prostate cancer (PCa) is a growing public health problem. The most recent estimates of the global incidence of PCa indicate that it is the third most common male cancer worldwide, accounting for about 10% of all cancer cases [10]. Although more common in the elderly, it occurs in men from middle age onwards, and presents a number of management dilemmas to the urologist. Prostate cancer is usually diagnosed using a combination of digital rectal examination of the prostate, serum prostate specific antigen (PSA) measurement and then prostate biopsy if indicated. Whilst there are some features of the disease which enable us to estimate prognosis (such as high grade, advanced stage), we are not able to confidently distinguish those cases of PCa which will cause a man morbidity or mortality from those that will not, particularly in those cases which are not advanced at presentation. Some countries, such as the USA, have adopted widespread screening programmes for PCa in asymptomatic men aged over 50 years. This has lead to an annual increase in PCa incidence rates from about 6% in the late 1980s to about 18% in the early 1990s [5]. Other countries, such as England and Wales, do not have a PSA screening programme yet there have been decreases in PCa mortality rates since the mid 1990s in both England and Wales and the USA, despite the differences in the use of screening between these regions [2]. The use of PSA screening detects (and therefore leads to the treatment of) PCa at an earlier stage, but the fact that there is no proven decrease in mortality from such an approach indicates that some cases are being unnecessarily treated. Furthermore, the radical (curative) treatments available for early PCa (most commonly radical prostatectomy, conformal radiotherapy or brachytherapy) carry a significant risk of morbidity and a small risk of mortality: unnecessary treatment is clearly undesirable. The clinical staging of PCa presents a further management problem. PCa is currently staged using a combination of clinical examination and imaging, along with consideration of tumour grade from biopsy results and PSA values. Cases with the highest chance of cure from radical treatment, particularly radical prostatectomy, are those in which the disease does not extend beyond the prostatic capsule. The imaging modality most commonly used for the local clinical staging of PCa is magnetic resonance imaging (MRI). However MRI has limitations in its ability to detect extra-prostatic disease [11], as do other imaging modalities such as transrectal ultrasound scanning (TRUS) of the prostate. TRUS is quick and easy to perform, and whilst it currently has no role in the staging of PCa, it is the modality used to guide needle biopsy of the prostate in men found to have a raised PSA and/or clinical suspicion of cancer. Hypoechoic areas within the prostate on TRUS are said to be suspicious of cancer, but the majority of hypoechoic areas prove not to be malignant on biopsy [4]. Also, half of non-palpable prostate tumours over 1cm in diameter are not visible on ultrasound [3]. Owing to these limitations, TRUS is most commonly used to guide accurate placement of the needle in prostatic biopsy. S. Phipps (&) Specialist Registrar in Urology, Ninewells Hospital and Medical School, Dundee, UK e-mail: SPhipps27@aol.com