Prostate cancer is frequently initially suspected through screening processes. (Refer to Screening Tests for Prostate Cancer for detailed information.) Early stages of prostate cancer often present without noticeable symptoms, yet more advanced cases can manifest through symptoms that prompt diagnosis.
If prostate cancer is considered a possibility based on screening results or the presence of symptoms, further diagnostic tests become essential for confirmation. Typically, individuals initially consulting their primary care physician might be directed to a urologist, a specialist focusing on disorders of the urinary and genital tracts, including prostate cancer.
The definitive diagnosis of prostate cancer is achieved through a prostate biopsy, which we will discuss in detail below. However, advancements in medical imaging, particularly Magnetic Resonance Imaging (MRI), have revolutionized the diagnostic pathway for prostate cancer. This article will delve into the crucial role of MRI in modern prostate cancer diagnosis, enhancing detection, guiding biopsies, and improving staging accuracy.
Initial Assessment: Medical History and Physical Exam
When prostate cancer is suspected, the initial steps involve a thorough gathering of your medical history and a physical examination. Your doctor will inquire about any symptoms you’ve experienced, such as changes in urinary habits or sexual function, and the duration of these symptoms. Furthermore, they’ll explore potential risk factors, including any family history of prostate cancer.
The physical exam often includes a digital rectal exam (DRE). In this procedure, the doctor inserts a gloved and lubricated finger into the rectum to physically examine the prostate gland for any irregularities, such as lumps or hardened areas, that might indicate cancer. The DRE can provide valuable information about the prostate’s size, shape, and consistency. It can also sometimes help determine if a potential cancer is confined to one side of the prostate, present on both sides, or possibly extending beyond the prostate to nearby structures. The doctor may also conduct a general physical examination to assess other areas of your body.
Following the physical exam, your doctor might order further tests, with the PSA blood test being a common next step.
PSA Blood Test: A Key Indicator
The prostate-specific antigen (PSA) blood test measures the level of PSA, a protein produced by both normal and cancerous cells within the prostate gland. While PSA is primarily found in semen, a small amount circulates in the bloodstream.
PSA Test in Prostate Cancer Suspicion
The PSA test serves a dual purpose. It’s utilized as a screening tool for prostate cancer in men without symptoms and as an initial diagnostic test for men presenting with symptoms suggestive of prostate cancer.
PSA levels in the blood are quantified in nanograms per milliliter (ng/mL). It’s important to understand that while the likelihood of prostate cancer increases with higher PSA levels, there isn’t a definitive PSA threshold that definitively confirms or excludes prostate cancer.
Many physicians use a PSA cutoff of 4 ng/mL or higher to prompt further investigation, while some might recommend additional testing at lower levels, such as 2.5 or 3 ng/mL, depending on individual risk factors.
- Most men without prostate cancer exhibit PSA levels below 4 ng/mL. However, it’s crucial to note that a PSA level below 4 ng/mL doesn’t guarantee the absence of cancer.
- Men with PSA levels between 4 and 10 ng/mL, often termed the “borderline range,” have approximately a 25% chance of having prostate cancer. Significantly, a considerable portion of these cancers may be low-grade and potentially not require immediate treatment (refer to “Prostate cancer grade,” below).
- When PSA levels exceed 10 ng/mL, the probability of prostate cancer rises to over 50%. Similar to the borderline range, some of these cancers may also be low-grade.
Elevated PSA levels often necessitate further diagnostic evaluation to determine the presence of prostate cancer. For a more comprehensive understanding of the PSA test, including factors influencing PSA levels, specialized PSA tests, and subsequent steps for abnormal results, please consult Screening Tests for Prostate Cancer.
PSA Test in Diagnosed Prostate Cancer
The PSA test also plays a vital role in managing men already diagnosed with prostate cancer.
- At the initial diagnosis, the PSA level, in conjunction with DRE findings and tumor grade (determined from the biopsy, discussed later), helps guide decisions regarding the need for additional staging tests like CT scans or bone scans.
- The PSA level contributes to determining the stage (extent) of the cancer. For localized cancers, PSA levels assist in categorizing the cancer into risk groups, influencing the selection of appropriate treatment options.
- PSA tests are crucial for monitoring treatment effectiveness and detecting potential cancer recurrence post-treatment. (See Following PSA Levels During and After Treatment.)
Prostate Biopsy: Establishing a Definitive Diagnosis
If PSA blood test results, DRE findings, or other assessments suggest the possibility of prostate cancer, a prostate biopsy is typically the next essential step.
A biopsy involves extracting small tissue samples from the prostate for microscopic examination. The core needle biopsy is the standard method for diagnosing prostate cancer and is typically performed by a urologist.
During the biopsy, the urologist usually employs an imaging technique, such as transrectal ultrasound (TRUS) or MRI, or a fusion of both, to visualize the prostate. A thin, hollow needle is rapidly inserted into the prostate, either through the rectal wall (transrectal biopsy) or through the perineum (skin between scrotum and anus, transperineal biopsy). As the needle is withdrawn, it retrieves a small core of prostate tissue. This process is repeated multiple times, typically yielding around 12 core samples from different prostate regions.
While the procedure might sound uncomfortable, each biopsy insertion usually causes only brief, mild discomfort due to the use of a spring-loaded biopsy instrument that rapidly inserts and retracts the needle. Local anesthesia is often administered to numb the area around the prostate, minimizing discomfort. It’s advisable to discuss pain management strategies with your doctor prior to the biopsy.
The biopsy procedure itself usually takes about 10 minutes and is commonly performed in a doctor’s office setting. Antibiotics are typically prescribed before and potentially after the biopsy to reduce the risk of infection.
Post-biopsy, some soreness in the area and blood in the urine are common for a few days. Light rectal bleeding, especially in individuals with hemorrhoids, can also occur. Many men experience blood in their semen, which can persist for several weeks depending on ejaculation frequency.
Biopsy Results and Interpretation
The biopsy samples are sent to a pathology lab where a specialized physician, a pathologist, examines them under a microscope to detect cancer cells. Pathology reports, containing the biopsy results, usually become available within 1 to 3 days, although it can sometimes take longer. The results are generally categorized as:
- Negative for cancer: No cancer cells were identified in the biopsy samples.
- Positive for cancer: Cancer cells were detected in the biopsy samples.
- Suspicious or atypical: Abnormalities were observed, but they may not definitively be cancerous. (Various types of suspicious and atypical findings are discussed below.)
Negative Biopsy Results and Further Steps
If the prostate biopsy is negative for cancer, and the overall suspicion of prostate cancer remains low based on PSA levels and other tests, no further testing beyond routine PSA tests (and possibly DREs) may be necessary at that time.
However, even with multiple samples, biopsies can occasionally miss cancer if the needles don’t happen to pass through cancerous tissue. This is termed a false-negative result. If clinical suspicion for prostate cancer remains high (e.g., very elevated PSA levels), your doctor might recommend:
- Additional lab tests (blood, urine, or biopsy sample analyses) to refine the risk assessment for prostate cancer. Examples include the Prostate Health Index (PHI), 4Kscore test, PCA3 tests (e.g., Progensa), and ConfirmMDx. These tests are discussed in What’s New in Prostate Cancer Research?.
- Prostate MRI (if not already performed) to identify suspicious areas within the prostate that warrant biopsy. This is where mpMRI becomes particularly valuable, as discussed below.
- Repeat prostate biopsy, potentially targeting different prostate regions or utilizing imaging guidance like MRI to focus on suspicious areas.
Prostate Cancer Grade: Gleason Score and Grade Groups
When prostate cancer is diagnosed via biopsy, it is assigned a grade. The grade reflects the degree of abnormality of the cancer cells under microscopic examination. Higher-grade cancers appear more abnormal and are associated with a greater propensity for rapid growth and spread. Prostate cancer grading is primarily described using two systems: the Gleason score and Grade Groups.
Gleason Score
The Gleason system, a long-established grading method, uses scores from 1 to 5 based on how closely the cancer cells resemble normal prostate tissue.
- Grade 1: Cancer cells closely resemble normal prostate tissue.
- Grade 5: Cancer cells appear highly abnormal.
- Grades 2-4: Represent intermediate levels of abnormality.
In practice, most prostate cancers are graded 3 or higher; grades 1 and 2 are rarely used.
Since prostate cancers often contain areas with varying grades, the Gleason score is derived by grading the two most prevalent cancerous areas within the tumor. These two grades are then summed to produce the Gleason score (or Gleason sum).
The first number in the Gleason score represents the predominant grade within the tumor. For instance, a Gleason score of 3+4=7 indicates that the majority of the tumor is grade 3, with a smaller portion being grade 4, totaling a Gleason score of 7.
While the Gleason score typically reflects the two most common grades, modifications exist in certain scenarios, such as when a biopsy sample contains a significant amount of high-grade cancer or includes three grades with high-grade cancer present. These modifications aim to capture the more aggressive nature of such cancers.
Theoretically, Gleason scores range from 2 to 10, but scores below 6 are uncommon. Based on Gleason scores, prostate cancers are broadly categorized into three groups:
- Gleason score ≤ 6: Often termed well-differentiated or low-grade. These cancers tend to grow slowly and have a low likelihood of spreading. Some experts even question whether these should be classified as true cancers.
- Gleason score = 7: Categorized as moderately differentiated or intermediate-grade.
- Gleason score 8-10: Designated as poorly differentiated or high-grade.
Grade Groups
Recognizing potential limitations of the traditional Gleason score in fully capturing the nuances of prostate cancer aggressiveness, clinicians have introduced Grade Groups, ranging from 1 (least aggressive) to 5 (most aggressive):
- Grade Group 1 = Gleason 6 (or less)
- Grade Group 2 = Gleason 3+4=7
- Grade Group 3 = Gleason 4+3=7
- Grade Group 4 = Gleason 8
- Grade Group 5 = Gleason 9-10
Grade Groups are likely to gradually replace the Gleason score as the primary grading system, although both might currently appear on pathology reports.
Additional Pathology Report Information
Beyond cancer grade, pathology reports often include other relevant details, such as:
- Number of biopsy cores containing cancer (e.g., “7 out of 12”).
- Percentage of cancer within each core.
- Laterality of cancer (unilateral – left or right side, or bilateral – both sides of the prostate).
Suspicious, Atypical, or Other Biopsy Findings
Sometimes, biopsy samples may not definitively show cancer but exhibit abnormalities that are not entirely normal.
Prostatic Intraepithelial Neoplasia (PIN): PIN involves changes in prostate cell appearance, but the abnormal cells haven’t invaded surrounding prostate tissue, unlike cancer cells. PIN is further classified into:
- Low-grade PIN: Prostate cell patterns appear nearly normal. Low-grade PIN is not considered a significant prostate cancer risk factor. Follow-up for low-grade PIN is usually similar to normal biopsy results.
- High-grade PIN: Cell patterns show more pronounced abnormalities. High-grade PIN is associated with an increased risk of developing prostate cancer over time. Careful monitoring and repeat biopsies (or risk-assessment lab tests like PHI, 4Kscore, PCA3, or ConfirmMDx) are often recommended, particularly if multifocal high-grade PIN (present in multiple prostate areas) is found or if the initial biopsy didn’t sample all prostate regions.
Intraductal Carcinoma: This involves prostate cancer cells growing into pre-existing prostate ducts. Intraductal carcinoma is frequently found alongside high-grade prostate cancer. Its presence on biopsy suggests a high likelihood of nearby high-grade prostate cancer, often prompting treatment with surgery or radiation therapy.
Atypical Small Acinar Proliferation (ASAP): Also termed glandular atypia or atypical glandular proliferation, or simply “suspicious for cancer.” These terms indicate cells that resemble cancer but are too few for definitive diagnosis. ASAP carries a significant risk of underlying prostate cancer, often leading to recommendations for repeat biopsy within a few months.
Proliferative Inflammatory Atrophy (PIA): PIA involves prostate cells smaller than normal with signs of inflammation. PIA is not cancerous, and its role in the development of high-grade PIN or prostate cancer is still under investigation.
Genetic and Molecular Testing of Prostate Cancer Cells
In cases of diagnosed prostate cancer, the cancer cells from the biopsy may undergo genetic or protein analysis to identify changes that could influence treatment decisions. For instance:
For localized prostate cancer, molecular or genomic tests on cancer cells can help predict cancer growth and spread rate. Tests like Decipher, Oncotype DX Prostate, Prolaris, and Promark assist in determining if active surveillance is suitable or if definitive treatment like surgery or radiation is preferable. Further details are available in Risk Groups and Lab Tests to Help Determine Risk for Localized Prostate Cancer.
For metastatic prostate cancer, genetic testing can identify specific gene or protein alterations that may make the cancer susceptible to targeted therapy drugs. For example, mutations in BRCA genes or other DNA repair genes can make PARP inhibitors a potential treatment option.
Genetic Testing for Hereditary Prostate Cancer Risk
Genetic counseling and testing for inherited gene changes are recommended for certain men with prostate cancer, particularly those with:
- Family history of known inherited gene mutations linked to prostate cancer risk (e.g., BRCA mutations, Lynch syndrome).
- Strong family history of prostate cancer or specific other cancers.
- Personal history of other cancers (especially breast cancer).
- Ashkenazi Jewish ancestry.
- Metastatic prostate cancer.
- High-risk prostate cancer or intraductal carcinoma.
- Prostate cancer with gene mutations (e.g., BRCA) potentially indicating a hereditary component.
More information can be found at Genetic Counseling and Testing for Prostate Cancer Risk.
Imaging Tests: Visualizing the Prostate and Beyond
Imaging tests utilize various technologies like X-rays, magnetic fields, sound waves, or radioactive substances to create internal body images. Imaging plays several roles in prostate cancer management:
- Detecting prostate cancer.
- Guiding procedures like biopsies and certain treatments.
- Assessing cancer spread to other body areas.
The specific imaging tests needed depend on the clinical situation. For example, MRI and/or TRUS are commonly used to guide prostate biopsies. In diagnosed prostate cancer, imaging may be needed to evaluate for metastasis. However, men with low-risk features (normal DRE, low PSA, low Gleason score) may not require extensive staging imaging due to the low probability of spread.
Commonly used imaging modalities for prostate cancer include:
Transrectal Ultrasound (TRUS)
TRUS involves inserting a finger-width probe into the rectum. The probe emits sound waves that generate echoes from the prostate. These echoes are processed into a black-and-white prostate image.
The procedure is typically quick (under 10 minutes), performed in a doctor’s office, and generally not painful, although some pressure may be felt. Local numbing is sometimes used.
TRUS applications in prostate cancer include:
- Detecting suspicious prostate areas in men with abnormal DRE or PSA (though it can miss some cancers).
- Guiding prostate biopsies, ensuring accurate needle placement.
- Measuring prostate size for PSA density calculation (see Screening Tests for Prostate Cancer).
- Guiding certain treatments like brachytherapy and cryotherapy.
Advanced TRUS techniques like color Doppler and micro-ultrasound are showing promise for enhanced diagnostic capabilities. (See What’s New in Prostate Cancer Research?)
Magnetic Resonance Imaging (MRI)
MRI scans utilize radio waves and strong magnets to produce detailed soft tissue images. MRI excels in providing high-resolution visualization of the prostate and surrounding tissues, making it a cornerstone in modern prostate cancer diagnosis. Contrast agents like gadolinium may be injected intravenously to enhance image detail.
MRI plays a multifaceted role in prostate cancer management:
- Risk Stratification and Biopsy Decision: Multiparametric MRI (mpMRI) is increasingly used to assess the likelihood of clinically significant prostate cancer in men with elevated PSA or suspicious DRE. It helps determine the need for prostate biopsy, potentially avoiding unnecessary biopsies in men with low suspicion on mpMRI.
A detailed MRI scan providing a clear image of the prostate, crucial for detecting and staging prostate cancer.
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Targeted Biopsy Guidance: MRI is invaluable for guiding prostate biopsies. MRI/ultrasound fusion biopsy combines pre-biopsy MRI images with real-time TRUS during the procedure. This fusion allows for targeted biopsies of suspicious areas identified on MRI, significantly increasing the detection rate of clinically significant prostate cancers compared to traditional systematic biopsies.
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Intra-Procedural MRI Guidance: MRI can also be used during a prostate biopsy procedure to directly guide needle placement in real-time.
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Staging and Local Extent Assessment: In diagnosed prostate cancer, MRI is crucial for local staging. It can assess if the cancer has extended beyond the prostate capsule, invaded the seminal vesicles, or involved other nearby structures (T-staging). This information is vital for treatment planning. However, MRI staging may not be routinely needed for low-risk, localized cancers.
To optimize MRI image quality, an endorectal coil may be placed in the rectum. This can cause some discomfort, and sedation may be offered if needed.
Multiparametric MRI (mpMRI): This advanced MRI technique is specifically designed for prostate cancer detection and characterization. mpMRI combines standard anatomical MRI with functional imaging sequences like:
- Diffusion Weighted Imaging (DWI): Assesses water molecule diffusion in tissues, which is often restricted in cancerous areas.
- Dynamic Contrast Enhanced (DCE) MRI: Evaluates blood flow and vascularity, often increased in tumors.
- MR Spectroscopy (MRS): Analyzes the chemical composition of tissues, detecting metabolic changes associated with cancer.
By integrating these parameters, mpMRI provides a comprehensive assessment of the prostate, improving cancer detection and risk stratification. mpMRI results are often reported using the Prostate Imaging Reporting and Data System (PI-RADS). PI-RADS assigns scores from 1 (very low suspicion of clinically significant cancer) to 5 (very high suspicion).
MRI/Ultrasound Fusion-Guided Prostate Biopsy: This technique leverages pre-biopsy mpMRI to identify suspicious prostate regions. During the biopsy, MRI images are fused with real-time TRUS images, guiding the biopsy needles to precisely target these suspicious areas. This targeted approach enhances the accuracy of prostate biopsies and improves the detection of clinically significant prostate cancers.
Bone Scan
Bone scans are used to detect prostate cancer spread to the bones, a common site of metastasis. A small amount of radioactive material is injected, which accumulates in areas of bone damage. A special camera detects the radioactivity and creates a skeletal image.
While bone scans can suggest bone metastasis, other non-cancerous conditions like arthritis can produce similar findings. Further investigations like plain X-rays, CT or MRI scans, or bone biopsy may be needed for confirmation.
Positron Emission Tomography (PET) Scan
PET scans are similar to bone scans, using radioactive tracers injected into the bloodstream. However, PET scans use tracers that preferentially accumulate in cancer cells.
Standard FDG-PET scans are not very effective for prostate cancer detection. However, newer PET tracers have shown improved results:
- Newer Tracers for Prostate Cancer PET: Fluciclovine F18, Sodium fluoride F18, Choline C11.
- PSMA PET Scans: Tracers targeting prostate-specific membrane antigen (PSMA), a protein highly expressed on prostate cancer cells, are particularly promising. Examples include Ga 68 PSMA-11 (Ga 68 gozetotide, Locametz, Illuccix, Gozellix), 18F-DCFPyl (piflufolastat F 18 or Pylarify), and 18F-rhPSMA-7.3 (flotufolastat F 18 or Posluma).
PSMA PET scans are increasingly used when the presence or location of prostate cancer spread is unclear, such as in cases of unclear bone scan results or rising PSA after treatment without a known recurrence site. PSMA PET scans can also help determine suitability for PSMA-targeted radiopharmaceutical therapy.
PET scan images are less detailed than MRI or CT, but they can detect cancer throughout the body. Combined PET-MRI or PET-CT scanners offer simultaneous PET and MRI/CT imaging for enhanced anatomical detail in areas identified on PET.
The optimal use of newer PET tracers is still evolving, and availability may vary across imaging centers.
Computed Tomography (CT) Scan
CT scans use X-rays to create detailed cross-sectional body images. CT scans are not routinely needed for localized prostate cancer but can be useful in assessing lymph node involvement or local recurrence after treatment.
CT scans are less effective than MRI for visualizing the prostate gland itself.
Lymph Node Biopsy
Lymph node biopsy, also known as lymph node dissection or lymphadenectomy, involves removing lymph nodes to check for cancer spread. It is not commonly performed for prostate cancer but may be used to assess lymph node metastasis.
Lymph Node Removal During Prostatectomy
During radical prostatectomy (surgical removal of the prostate), pelvic lymph nodes may be removed if there is a significant risk of cancer spread based on PSA levels or Gleason score. The lymph nodes and prostate are then examined pathologically.
Lymph Node Biopsy as a Separate Procedure
Lymph node biopsy as a standalone procedure is rare. It might be considered when radical prostatectomy isn’t planned (e.g., radiation therapy) but lymph node status is crucial.
Needle biopsy guided by imaging (MRI or CT) is the most common approach for separate lymph node biopsy. Local anesthesia is used, and the needle sample is sent for pathological analysis.
Conclusion: The Evolving Landscape of Prostate Cancer Diagnosis with MRI
Prostate cancer diagnosis has evolved significantly, with MRI emerging as a central imaging modality. From risk stratification and guiding targeted biopsies to local staging and recurrence detection, MRI offers unparalleled visualization and characterization of the prostate. Multiparametric MRI and MRI-guided biopsy techniques have revolutionized the accuracy of prostate cancer detection and diagnosis, leading to more personalized and effective management strategies. While other imaging modalities like TRUS, bone scans, and PET scans remain valuable in specific clinical scenarios, MRI’s role in the diagnostic pathway is undeniable and continues to expand, ultimately improving outcomes for men facing prostate cancer. Early detection and consultation with a urologist remain paramount for optimal prostate cancer management.
- Written by
- References
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.
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Last Revised: March 21, 2025
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