T2 weighted MRI shows a hypointense lesion (a region of low signal that appears relatively darker) with restricted diffusion. There is low ADC (which stands for ‘Apparent diffusion coefficient’ and measures the magnitude of dispersal of water molecules within the tissue), and increased K trans (K trans is a measure of capillary permeability). Findings: Typical features of prostate cancer on MRI.
The prostate carcinoma in Image 1 is located anteriorly adjacent to the urethra. The position of this tumour is notoriously difficult to diagnose on TRUS (trans-rectal ultrasound) biopsy because this procedure usually targets the peripheral and central zones of the prostate.
The patient, whose case is demonstrated in Image 1 above, was a 55 year old gentleman who presented with persistent elevation of PSA (prostate-specific antigen) which is a protein produced by the epithelial cells of the prostate gland. Some PSA enters the bloodstream and high levels can be an indicator of prostate cancer. Initial routine TRUS biopsy results were negative, (as were follow-up saturation TRUS biopsy results) although this patient had a positive histology result on transperineal guided biopsy ( in this type of biopsy the needle is passed through the skin of the perineum parallel to the prostate) which allows examination and access to all areas of the prostate gland.
This case is a very good example of why MRI is so useful in prostate cancer screening and detection. PSA screening remains controversial as an elevated PSA can be due to other factors, such as benign enlargement of the prostate which is also quite common in older men. Furthermore, many prostate cancers develop so slowly that treatment is not indicated and invasive diagnostic procedures, such as biopsies, can cause unnecessary risk. Likewise, a non-elevated PSA does not always indicate an absence of prostate cancer. TRUS biopsies, as demonstrated in the above case, are essentially samples that are taken blind as some cancers cannot be seen with ultrasound. Initial biopsies can miss 20 – 30% of clinically significant cancers.(1) MRI has been used to improve identification of and more accurately stage prostatic cancers.(2)
Adenocarcinoma occurs in the cells of glands and is the most common type of prostatic cancer, 95% of all prostate cancers are adenocarcinomas.(3) Histology results from biopsy are graded according to the Gleason score. The most prevalent types of dysplasia (or cell abnormalities) are given a score from 1 -5 and the second most prevalent type are given a score on the same criteria; the two figures are then added together to give the Gleason score which is between 2 and 10, with 10 being the most aggressive. Prostate tumours are also graded by a process called ‘TMN’ which stands for Tumour size, nodal involvement and distant metastases (or secondary spread). The ‘T’ partof the tumour is graded thus:- T1 tumours are too small to be seen; T2 tumours are confined within the prostate gland; T3 tumours have broken outside of the covering (or capsule) of the prostate and T4 type tumours have spread to neighbouring areas. Nodal involvement is dependant on whether (or not) the cancer cells have spread to neighbouring lymph nodes and the distant metastases is graded according to spread, or lack of, outside of the pelvis.
MRI Examinaton. Tranverse T2 weighted image. Prostate cancer located in the right anterior section of the gland also involves the transition and peripheral zones. 57 year old patient with a raised PSA an a Gleason score of 7 (3+4)
Prostatic carcinoma is the most common malignant tumour in men and the second most common cause of cancer-related deaths.(4) Cancer of the prostate is a disease that mainly affects older men, the average age at diagnosis is 70(5) although a lot of men will never know that they have prostatic cancer and it is discovered on autopsy. Cancer of the prostate is a very common condition increasing in prevalence with advancing age. Autopsy studies of Chinese, German, Israeli, Jamaican, Swedish, and Ugandan men who died of other causes found prostate cancer evident in 30% of men in their 50s, and in 80% of men in their 70s.(6)
1. PROMIS – Prostate MRI Imaging Study. An evaluation of multi-parametric magnetic resonance imaging in the diagnosis and characterisation of prostate cancer. (UK) Medical Research Council – Clinical Trials Unit – PROMIS Trials Office. MRC: PR11, 2 February 2012
2. Taira, A. V., Merrick, G. S., Galbreath, R. W., Andreini, H., Taubenslag, W., Curtis, R., et al. (2010). Performance of transperineal template-guided mapping biopsy in detecting prostate cancer in the initial and repeat biopsy setting. Prostate cancer and prostatic diseases, 13(1), 71–77. doi:10.1038/pcan.2009.42
3. Bonekamp D, Jacobs MA, El-Khouli R et-al. Advancements in MR imaging of the prostate: from diagnosis to interventions. Radiographics. 2011;31 (3): 677-703. doi:10.1148/rg.313105139 – Free text at pubmed – Pubmed citation.
4. 1. Bartolozzi C, Selli C, Olmastroni M et-al. Rhabdomyosarcoma of the prostate: MR findings. AJR Am J Roentgenol. 1988;150 (6): 1333-4. AJR Am J Roentgenol (citation) – Pubmed citation
5. 2. Hankey BF, Feuer EJ, Clegg LX, Hayes RB, Legler JM, Prorok PC, Ries LA, Merrill RM, Kaplan RS (June 16, 1999). “Cancer surveillance series: interpreting trends in prostate cancer—part I: Evidence of the effects of screening in recent prostate cancer incidence, mortality, and survival rates”. J Natl Cancer Inst 91 (12): 1017–24
6.3. Breslow N, Chan CW, Dhom G, Drury RA, Franks LM, Gellei B, Lee YS, Lundberg S, Sparke B, Sternby NH, Tulinius H (November 15, 1977). “Latent carcinoma of prostate at autopsy in seven areas. The International Agency for Research on Cancer, Lyons, France”.Int J Cancer 20 (5): 680–8. doi:10.1002/ijc.2910200506. PMID 924691.