Prostate cancer is a common malignant disease seen in men, which accounts for almost one-third every year of all the new diagnoses made for cancer. When this disease is detected in its early stages, before it has spread, it can be treated through prostatectomy or radiotherapy. However, the current diagnostic methods of early diagnosis and screening have certain downsides and are a topic of much debate.
An example of this is the PSA or prostate-specific antigen test, which is utilized as a screening test. This blood test has a fairly high false-positive rate, leading to overtreatment and invasive test procedures which are not really necessary.
Owing to this reason, the PSA test has been critically debated about by the Preventive Services Task Force, USA, recommending that this test not be used for screening prostate cancer.
The prostate needle biopsy is the gold standard to confirm the diagnosis for prostate cancer. This biopsy involves the retraction of samples of tissue using a needle in about 6 to 18 places within the prostate gland in order to get a true representative of the sample tissue. Transrectal ultrasound (TRUS) is commonly employed as a guide in this procedure. This ultrasound technique is cost effective and available round the globe.
However, the information provided, in addition to the basics, in this ultrasound is limited and it also results in low sensitivity results with the predictive positive value being low as well. This means that many biopsies may be required which can cause discomfort and also increase the rate of side effects such as infection, hematuria, and rectal bleeding.
Therefore, imaging techniques can be used as guide needle biopsy or assist in prostate cancer screening to decrease the various risk factors posed by needle biopsies, and thus enhance early detection of the disease.
Alternative Diagnostic Methods
The gold standard TRUS cannot be used for the detection of prostate cancer due to its low sensitivity. Also, when it is used in image-guided biopsy, the results seem to vary considerably based on the instrument that is being used and also from one user to another.
Recent studies have suggested the use of qualitative ultrasound (QUS) technique for precise characterization of prostate cancer in about 15 patients. This technique removes the differences related to TRUS by standardizing the signals produced by the ultrasound in a manner that is dependent on frequency.
These signals are then tested against certain reference signals. Before radical prostatectomy, the patients were made to undergo QUS in this study. The histopathological specimens of whole-mounts were used to identify the areas affected by cancer and these were correlated with QUS images.
The researchers were able to obtain high levels of correlation between the QUS-detected stage of the disease and the results obtained from histopathological examination. This diagnostic method also revealed that in a given model, the extent of the disease predicted using QUS also predicted the histopathological disease extent.
This revelation was not observed with other markers such as Gleason score and PSA. The researchers were able to deduct that their observations show the ability of QUS to detect and define cancer of the prostate using non-invasive methods.
It has been concluded that such diagnostic procedures, when supported histopathologically, can aid in early diagnosis of the disease and also identify patients having prostate cancer at high-risk forms.
Magnetic resonance imaging or MRI is yet another approach to guide invasive procedures relating to prostate cancer such as biopsies or targeted radiotherapy. Elastography used in this method helps differentiate stiffening of localized tissue caused by cancer from normal healthy tissue.
A specimen of the whole prostate was obtained from a prostate cancer patient. The specimen was histopathologically analyzed in four slices and compared them to MRI as well as MRE (magnetic resonance elastography) images.
Researchers were able to determine that only certain regions of the tumor could be detected using MRI, whereas MRE can detect all regions affected by the tumor.
In addition to this, images obtained from histopathology revealed that muscular tissue was stiffer than normal healthy tissue just like the stiffness of the tumor tissue. Therefore, great care must be taken while using MRE with regard to sensitivity to differentiate tumorous tissue from healthy tissue.
Flexible Technology Accelerates Prostate Cancer Research
Digital Pathology technology of Huron was used to validate the above-mentioned techniques. TissueScope LE complete slide scanner from Huron automates the scanning process of varying slide sizes from 1” x 3” to 6” x 8” at a magnification up to 40x.
This scanner is used to scan whole mounts of brain, breast, or prostate sections. For more extensive research projects, Huron's LE 120 TissueScope scanner utilizes an autoloader for continuous, higher throughput, unattended scanning procedures.
McGrath DM et al. (2011) Biomechanical Property Quantification of Prostate Cancer by Quasi-static MR Elastography at 7 Telsa of Radical Prostatectomy, and Correlation with Whole Mount Histology. Proc Intl Soc Mag Reson Med. 19: 1483.
Mousavi SR (2014) Biomechanical Modeling and Inverse Problem Based Elasticity Imaging for Prostate Cancer Diagnosis. PhD thesis. Western University, Ontario.
Mousavi SR et al. (2014) Prostate clinical study of a full inversion unconstrained ultrasound elastography technique. Proc SPIE; 9040: 904004. doi: 10.1117/12.2043086.
Sadeghi-Naini A et al. (2015) Quantitative Ultrasound Spectroscopic Imaging for Characterization of Disease Extent in Prostate Cancer Patients. Translational Oncology; 8: 25-34. doi: 10.1016/j.tranon.2014.11.005.
About Huron Digital Pathology
Based in Waterloo, Ontario, Canada, Huron Digital Pathology has a 20 year history designing sophisticated imaging instrumentation. Our end-to-end digital whole slide imaging solutions for digital pathology incorporate our award-winning TissueScope™ digital slide scanners; TissueView™ image viewing, sharing and management platform; and our workflow-enhancing accessories, which include our innovative TissueSnap™ preview scanning station.
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