Advancements in Prostate Cancer Detection and Diagnosis

Introduction

Transrectal ultrasound (TRUS) imaging has traditionally been used to collect tissue samples for prostate cancer diagnosis. This procedure involves inserting needles into the prostate gland in various locations while guided by transrectal ultrasound (TRUS) imaging. The term "systemic biopsy" is also used to describe this. However, ultrasound does not always reveal the precise prostate cancer location; instead, it ensures that biopsy needles enter the gland safely.

As a result, ultrasound-guided biopsy samples might fail to identify low-grade cancer and areas of high-grade, potentially aggressive cancer. As a result, practitioners may suggest unnecessary treatments, leading to overtreatment. Therefore, there is a strong need for more advanced diagnostic techniques to detect and diagnose prostate cancer.

What Are the Drawbacks of Transrectal Ultrasound Imaging (TRUS)?

• Transrectal ultrasound-guided biopsy has historically been used to detect suspected malignant transformation proliferation and local staging sites. However, this method fails to see a large percentage of prostate cancers.

• Around 50 percent of prostate cancers appear hypoechoic, but up to 30 percent are isoechoic to the nearby normal tissue and are challenging to detect.

• Furthermore, only one-third of hypoechoic lesions develop into prostate cancer, making only about 40 percent of prostate cancers detectable on ultrasonography.

What Are the Advances in Prostate Cancer Detection?

Among the most recent advances in prostate cancer detection are the use of:

1. Multiparametric MRI (mpMRI):

• Transrectal ultrasound (TRUS) guided biopsy has been used in men and has shown low sensitivity and specificity for the detection of prostate cancer.

• As a result, biopsies performed throughout the prostate result in a high false-negative rate, misrepresentation of the actual tumor, and the possibility of complications such as urinary tract infection, gram-negative bacteremia, dysuria, and pain or discomfort.

• Multiparametric MRI (mpMRI) utilizes imaging alone to screen prostate cancer in men.

• It is suggested that if one in every four men could avoid prostate biopsy, multiparametric MRI (mpMRI) can be used as a triage test.

• However, if multiparametric MRI (mpMRI) is not clear in detecting cancer tissue, an image-guided biopsy is still required.

• Contrast-enhanced T1 and T2-weighted (CE-T1WI) magnetic resonance imaging (MRI) and dynamic gadolinium-enhanced imaging with a 1.5 Tesla scanner and phased pelvic array are used in prostate magnetic resonance imaging.

Advantages of multiparametric MRI (mpMRI):

1. It is superior to TRUS-guided biopsy to detect men at risk for prostate cancer.

2. Avoids the need for repeat biopsies.

3. It is susceptible and can predict negative values.

Disadvantage:

1. Expensive.

2. Time-consuming.

2. Multiparametric Ultrasound: Multiple other ultrasound techniques developed in an attempt to overcome the shortcomings of transrectal ultrasound imaging are:

3. Color and Power Doppler Ultrasound:

Prostate cancer progresses to a clinically significant level by forming new blood vessels (angiogenesis). Thus, color and power Doppler ultrasound can aid in detecting tissues with increased blood flow (hyperemic tissue) and, as a result, detect potential prostate cancer. However, the drawback of both the Dopplers is that neither of them is sensitive enough to detect early-stage prostate cancer due to the following:

• The low resolution of ultrasound.

• Vessels in the millimeter range are detected, whereas angiogenesis can result in vessels as small as 10 to 50 micrometers.

As a result, the utility of color and power Doppler ultrasonography may be limited to detecting only tumors with higher Gleason grades.

4. Contrast-Enhanced Ultrasound (CEUS):

• It is a newer technique not yet commonly used in clinical settings.

• It entails injecting gas-filled microbubbles (the size of erythrocytes) intravenously before or during ultrasound image acquisition.

• The injected microbubbles increase the backscatter of ultrasound waves, causing signals from blood flow to amplify.

• The ultrasound transducer detects these regions and generates images.

• Even in its early stages, prostate cancer has increased blood flow due to the formation of new blood vessels, and contrast-enhanced ultrasound (CEUS) will show:

1. Asymmetric rapid inflow.

2. Increased focal enhancement.

3. Asymmetry of blood vessels.

• A peak intensity value, similar to the degree of enhancement, is calculated using an algorithm and helps differentiate between benign and malignant lesions.

• These detections are beyond the resolution of traditional techniques such as color and power Doppler.

5. Ultrasound Elastography: This ultrasound is promising sonography currently used to stage chronic liver disease and has multiple other potential uses. The two types of ultrasound elastography are:

6. Shear Wave Elastography (SWE):

• It detects the stiffness of prostate cancer in comparison to normal tissue and can aid in the differentiation of neoplastic lesions.

• It produces less diagnostic variation as it solely depends on Young's modulus and the pulse transmitted by the ultrasound transducer.

• A recent study on shear wave elastography (SWE) mentioned its accuracy in detecting prostate cancer comparable to multiparametric MRI (mpMRI).

• This implies that they may help elucidate targets during ultrasound-guided biopsies on their own.

7. Strain Elastography (SE): It results in more variability as it relies on transducer compression, resulting in significant interobserver variability.

8. Prostate-Specific Membrane Antigen-Directed Positron Emission Tomography (PSMA-PET)-

• The cell surface of healthy prostate tissue contains prostate-specific antigen (PSA), which is significantly overexpressed in prostate cancer. As a result, this antigen was chosen as a target for prostate cancer imaging.

• For the detection of cancer, the prostate-specific antigen (PSA) is tagged with radioactive substances such as:

1. Indium 111.

2. 68 gallium.

3. C-11 choline.

4. F-18 fluciclovine.

• Indium 111-tagged prostate-specific antigen (PSA) had limited utility in diagnosing seminal vesicle and prostate gland tumors because it could not internalize viable prostate epithelial cells.

• In contrast, 68 gallium-labeled PSMA exhibits high tumor-to-background contrast and has aided in detecting primary prostate tumors.

• 68 gallium-prostate-specific membrane antigen-directed positron emission tomography (PSMA-PET) is perceived to be most helpful in detecting disease in patients with the primary staging of high-risk disease and biochemical recurrence.

• It may also be helpful for biopsy targeting after a previous negative biopsy in a patient with a high suspicion of prostate cancer, especially when combined with mpMRI.

• According to the National Comprehensive Cancer Network (NCCN), prostate-specific membrane antigen-directed positron emission tomography (PSMA-PET) scan can be used in patients with PSA persistence or recurrence status after radical prostatectomy using either C-11 choline or F-18 fluciclovine.

What Is the Significance of Early Prostate Cancer Detection?

• Early diagnosis for men with specific inherited genetic traits will aid in determining a steadily increasing chance of developing prostate cancer. However, there are no clear guidelines for when, how, or whether to screen men at high genetic risk for prostate cancer.

• Magnetic resonance imaging (MRI) of the prostate has been used to learn more about the early occurrence of these cancers. However, it is also pertinent to know whether regular scans can detect cancers early before they spread to other body parts.

Conclusion

Emerging technology advancements are altering the approach to detecting and diagnosing prostate cancer. For example, prostate-specific membrane antigen-directed positron emission tomography (PSMA-PET) helps diagnose prostate cancer and recurrence in patients with conventional negative imaging. In addition, Multiparametric MRI (mpMRI) is useful in risk-stratifying patients with suspected prostate cancer and will be the foundation for future prostate cancer imaging. Overall, new imaging technology will soon allow for more accurate diagnosis, staging, and treatment follow-up in prostate cancer patients.