Prostate Cancer

Quick Answer

PSMA-PET is the most sensitive imaging for prostate cancer, outperforming conventional imaging (CT + bone scan) for nodal and distant disease at both initial staging of high-risk disease and biochemical recurrence, often at low PSA. In metastatic castration-resistant disease (mCRPC), PSMA-PET is also the companion diagnostic that selects patients for ¹⁷⁷Lu-PSMA-617 radioligand therapy; ²²³Ra-dichloride is an option for symptomatic bone-dominant disease without visceral metastases. Prostate cancer is the archetypal nuclear-medicine theranostic solid tumor: the same target (PSMA) is imaged to select, and then irradiated to treat.

Definition

Prostate cancer is a malignant epithelial neoplasm arising from the glandular (acinar) epithelium of the prostate, the overwhelming majority being acinar adenocarcinoma. It spans a biological continuum from indolent, screen-detected, organ-confined disease that may never threaten life, to lethal metastatic castration-resistant cancer and its highly aggressive neuroendocrine / small-cell variants.

Synonyms

Prostatic adenocarcinoma; prostate carcinoma; carcinoma of the prostate. Disease-state descriptors in common use: localized, biochemically recurrent (BCR), metastatic hormone-sensitive (mHSPC) / castration-sensitive (mCSPC), non-metastatic castration-resistant (nmCRPC), and metastatic castration-resistant (mCRPC).

Epidemiology

Prostate cancer is the most commonly diagnosed non-cutaneous malignancy in men worldwide and a leading cause of male cancer death. Incidence rises steeply with age; most diagnoses occur after age 65, and clinically undiagnosed histologic cancer is present in a large fraction of older men at autopsy. Risk is meaningfully higher, and disease tends to be more aggressive and present younger, in men of African ancestry. First-degree family history and germline DNA-repair mutations (notably BRCA2) raise both risk and lethality. Widespread PSA screening produced a large stage-migration toward localized disease and a rise in incidence; screening intensity, and therefore incidence trends, vary by region and era.

Etiology & Risk Factors

• Non-modifiable: advancing age, African ancestry, family history, and germline mutations in DNA-damage-repair (DDR/HRR) genes — BRCA2 (strongest), BRCA1, ATM, CHEK2, PALB2 — and HOXB13 (G84E). Lynch-syndrome (mismatch-repair) carriers have modestly increased risk and MSI-high tumors.
• Probable/weaker: obesity and metabolic syndrome (associated with higher-grade disease and worse outcomes), possibly dietary and inflammatory factors.
• Androgen exposure is permissive but is not a simple linear risk factor.

Pathophysiology

Prostate adenocarcinoma is fundamentally an androgen-receptor (AR)–driven disease. Most cancers arise in the peripheral zone (a reason they are palpable on DRE and targetable by posterior-approach biopsy), with a minority in the transition zone. Tumor growth depends on AR signaling, which is why androgen-deprivation therapy (ADT) is the therapeutic backbone.

Progression to castration resistance occurs despite castrate serum testosterone through mechanisms that reactivate AR signaling: AR amplification and gain-of-function mutations, intratumoral (intracrine) androgen synthesis, constitutively active AR splice variants (AR-V7), and glucocorticoid-receptor bypass. A separate route is lineage plasticity — loss of AR dependence with transdifferentiation toward a neuroendocrine / small-cell phenotype, typically after intense AR-pathway inhibition and associated with combined RB1 and TP53 loss. This matters directly to imaging: neuroendocrine dedifferentiation tends to lose PSMA expression and gain FDG avidity.

Genetics & Molecular Biology

• Early/founder events: TMPRSS2–ERG gene fusion (present in roughly half of cases, placing an ETS oncogene under androgen-responsive control), PTEN loss (PI3K/AKT activation, adverse), SPOP mutations (a distinct molecular subclass).
• Progression events in CRPC: AR amplification/mutation/splice variants, TP53 and RB1 loss (linked to neuroendocrine transformation), MYC amplification.
• Actionable alterations: HRR/DDR defects (BRCA2 etc.) predict sensitivity to PARP inhibitors and platinum; MSI-high / dMMR (a small minority) predicts response to pembrolizumab; PTEN loss is being explored for AKT inhibition.
• PSMA (FOLH1 / GCPII): expression generally increases with grade, stage, and castration resistance — the molecular basis for PSMA theranostics — but is heterogeneous and is often lost in neuroendocrine/small-cell disease.

Histopathology & Grading

The dominant histology is acinar adenocarcinoma. Grade is assigned by the Gleason architectural pattern and reported as the modern ISUP / WHO Grade Group system, which is more intuitive and prognostically cleaner:

Cribriform architecture and intraductal carcinoma are adverse features. Aggressive variants include ductal adenocarcinoma and neuroendocrine / small-cell carcinoma (frequently PSMA-low, FDG-avid, and clinically fulminant). Immunohistochemistry (AMACR positive; basal markers p63/HMWCK lost in cancer) supports the diagnosis.

Clinical Presentation

Most localized disease is asymptomatic and detected through PSA testing or DRE. Locally advanced disease may cause lower-urinary-tract symptoms, hematuria, or hematospermia. Metastatic disease characteristically produces bone pain, and — because bone metastases are typically osteoblastic and marrow-infiltrating — anemia, cytopenias, and pathologic fractures; spinal cord compression is an oncologic emergency. Visceral (liver, lung) and lytic metastases are less common and flag more aggressive or neuroendocrine biology.

Laboratory Findings

• PSA (total, with free/total ratio, density, and velocity used to refine biopsy decisions) — the central marker for detection, response, and recurrence. Biochemical recurrence after prostatectomy is conventionally PSA ≥ 0.2 ng/mL (rising); after radiotherapy, the Phoenix definition is nadir + 2 ng/mL.
• Serum testosterone to confirm the castrate level (< 50 ng/dL) that defines castration resistance.
• Alkaline phosphatase and LDH (bone burden / prognosis); chromogranin A / NSE if neuroendocrine transformation is suspected.
• Germline and tumor genomic testing (HRR, MMR) in metastatic disease for therapy selection.

Imaging Findings by Modality

• Multiparametric MRI (mpMRI): primary tool for intraprostatic detection and local staging, scored by PI-RADS; guides targeted biopsy and assesses extracapsular extension / seminal-vesicle invasion.
• CT: insensitive for local disease and for early nodal/marrow metastases; used for gross nodal/visceral disease and radiotherapy planning.
• Ultrasound (TRUS): biopsy guidance (increasingly MRI-fusion); micro-ultrasound is emerging.
• Bone scan (Tc-99m-MDP/HDP SPECT): conventional detection of osteoblastic metastases; can show a superscan (diffusely intense skeleton with faint kidneys) in heavy burden, and a post-treatment flare. Sensitivity is limited at low tumor burden.
• PSMA-PET/CT (or PET/MRI): the most sensitive whole-body modality — superior to CT + bone scan for nodal and distant disease and the reference for staging high-risk disease and localizing recurrence.
• NaF-PET: highly sensitive for osteoblastic bone metastases but non-specific (any osteoblastic reaction) and bone-only.
• FDG-PET: limited in typical adenocarcinoma; valuable in dedifferentiated / neuroendocrine disease and to reveal PSMA-discordant lesions before radioligand therapy.

Radiopharmaceutical Uptake Mechanisms

PSMA (prostate-specific membrane antigen) is the type II transmembrane glycoprotein glutamate carboxypeptidase II (GCPII / FOLH1). Small-molecule urea-based inhibitors bind its extracellular enzymatic pocket and are internalized, concentrating tracer in PSMA-expressing cells. Expression rises with grade and castration resistance (favoring theranostics) but is heterogeneous and lost in neuroendocrine disease. PSMA is not prostate-specific: physiologic expression in salivary/lacrimal glands, kidneys, small bowel, and autonomic ganglia (celiac ganglion), and neovascular expression in many other tumors, underlies characteristic false positives. Bone-scan diphosphonates adsorb to hydroxyapatite at sites of osteoblastic turnover (an indirect, reactive signal). FDG reflects glucose-metabolic (GLUT/hexokinase) activity, elevated in dedifferentiated disease.

Typical PET Tracers

Typical SPECT Tracers

• Tc-99m-MDP / HDP — bone scintigraphy for osteoblastic metastases (widely available; SPECT/CT improves specificity).
• Tc-99m-PSMA (PSMA I&S) — SPECT PSMA imaging and radioguided surgery where PET is unavailable.
• (Historical) In-111-capromab pendetide (ProstaScint) — an obsolete anti-PSMA antibody SPECT agent, now supplanted by small-molecule PSMA PET.

Therapy Indications

• Localized: active surveillance (GG1 / low-volume GG2), radical prostatectomy, or radiotherapy ± ADT by risk.
• mHSPC: ADT intensified with an androgen-receptor pathway inhibitor (ARPI: abiraterone, enzalutamide, apalutamide) ± docetaxel ("doublet/triplet").
• nmCRPC: ARPI (apalutamide, enzalutamide, darolutamide) to delay metastasis.
• mCRPC: ARPI, docetaxel/cabazitaxel, ²²³Ra (symptomatic bone-only), ¹⁷⁷Lu-PSMA-617 (PSMA-positive), PARP inhibitors (HRR/BRCA), pembrolizumab (MSI-high), and sipuleucel-T.
• Neuroendocrine/small-cell disease is treated on a platinum-chemotherapy paradigm rather than AR-directed therapy.

Theranostics

Prostate cancer is the flagship image-and-treat solid tumor. PSMA-PET selects patients whose disease sufficiently expresses the target; ¹⁷⁷Lu-PSMA-617 then delivers β-radiation to the same target.

• VISION established an overall-survival benefit for ¹⁷⁷Lu-PSMA-617 plus standard care in PSMA-positive mCRPC after ARPI and taxane; PSMAfore supported benefit in the pre-taxane post-ARPI setting (label subsequently expanded).
• Patient selection uses PSMA-PET positivity (± FDG to exclude significant PSMA-negative/FDG-positive disease that would escape treatment).
• Dose-limiting organs are the salivary glands (xerostomia) and kidneys; marrow toxicity accrues, especially when sequenced with Ra-223.
• Response is judged by PSA together with imaging criteria (RECIP 1.0, built on PROMISE).
• α-emitter approaches (²²⁵Ac-PSMA-617) are investigational, including for Lu-177-refractory disease, with salivary toxicity a key limitation.

Differential Diagnosis (of PSMA-avid findings)

Because PSMA is not prostate-specific, several benign and non-prostatic entities mimic metastatic disease: the celiac (and other autonomic) ganglia (mimic retrocrural nodes), healing ribs/fractures and degenerative bone, Paget disease and fibrous dysplasia, benign thyroid nodules, and PSMA-expressing neovasculature in other tumors (renal cell, hepatocellular, thyroid, glioma). Ganglia are recognized by their typical paravertebral location, band/teardrop shape, and lack of a CT correlate.

Reporting Checklist

• Agent, injected activity, uptake time, and reference-organ uptake (blood pool, liver, parotid).
• Standardized framework: PROMISE molecular-imaging TNM (miTNM) and PSMA-RADS lesion-level certainty (1 → 5).
• Index-lesion SUVmax and overall tumor volume where relevant to therapy selection.
• Explicit statement of PSMA-positivity for RLT eligibility and of any FDG-discordant disease if a paired study was done.
• Benign mimics addressed (e.g. "paravertebral uptake consistent with celiac ganglion, not nodal").

Prognosis

Localized low-risk disease has excellent long-term survival, often without any treatment (active surveillance). Prognosis worsens with higher Grade Group, stage, and PSA, and with transition through mHSPC → CRPC. In advanced disease, metastatic burden and PSMA-PET tumor volume are prognostic, as are DDR status and the emergence of neuroendocrine transformation, which carries a poor outlook. Nomograms and the CAPRA/D'Amico frameworks integrate clinicopathologic variables for localized risk.

Board Pearls

PSMA-PET now spans the whole disease course — staging high-risk localized disease (proPSMA: PET/CT superior to CT + bone scan), localizing biochemical recurrence even at low PSA, and selecting and monitoring ¹⁷⁷Lu-PSMA therapy (VISION, PSMAfore; RECIP response) — while paired FDG flags dedifferentiated, PSMA-low disease that predicts poorer radioligand-therapy benefit.

For symptomatic bone-metastatic mCRPC without visceral disease, ²²³Ra improves survival (ALSYMPCA) but targets the bone microenvironment, so PSA is not a reliable response marker — follow alkaline phosphatase and skeletal/clinical endpoints, avoid concurrent abiraterone/prednisone (ERA-223), and mind cumulative marrow dose when sequencing with Lu-177-PSMA.

PSMA expression increases with grade and castration resistance (enabling theranostics) yet is lost with neuroendocrine transformation — the same lineage plasticity (RB1/TP53 loss) that raises FDG avidity. This is why a discordant FDG-positive / PSMA-negative phenotype both predicts poorer Lu-177-PSMA benefit and should prompt consideration of a neuroendocrine biopsy and platinum-based therapy.

Related Pages

• Tracer: PSMA PET agents (biodistribution, PROMISE/PSMA-RADS, detection-by-PSA).
• Therapy: ¹⁷⁷Lu-PSMA-617 (VISION/PSMAfore, dosimetry, salivary/renal dose) and ²²³Ra-dichloride.
• Recurrence workflow: PSMA & biochemical recurrence.
• Response criteria: Theranostics response criteria (RECIP/PROMISE/PCWG3).
• Related disease: Neuroendocrine tumors (for the neuroendocrine-transformation overlap).

Figure / Diagram Suggestions

• A schematic of the PSMA theranostic loop: PSMA-PET selection → ¹⁷⁷Lu-PSMA-617 therapy → PSA/RECIP response.
• PSMA molecule cartoon: extracellular GCPII domain, urea-based inhibitor binding, internalization.
• A disease-state timeline (localized → mHSPC → nmCRPC → mCRPC) annotated with the imaging and therapy decision points.
• Annotated PSMA-PET normal biodistribution / benign mimics plate (salivary, kidneys, bowel, celiac ganglion).

Common Pitfalls

• Treating a negative FDG-PET as excluding disease: typical AR-driven adenocarcinoma is often FDG-low, so FDG is informative chiefly in high-grade/dedifferentiated or neuroendocrine disease and for PSMA-discordant lesions — not for routine staging.
• Intense urinary tracer excretion into the bladder and ureters (FDG and, conceptually, PSMA) obscuring local recurrence and pelvic nodes — use delayed/diuretic imaging or careful anatomic correlation.
• Bone-scan flare after effective therapy — new or more intense osteoblastic uptake at healing lesions in the first months — misread as progression; interpret against PSA trajectory and follow-up.
• A superscan (diffusely intense skeleton with faint kidneys/soft tissue) mistaken for a normal or degenerative study when it actually signals heavy metastatic burden.
• Inflammatory/benign FDG uptake (recent biopsy, prostatitis, treated marrow) over-called as malignant.

Self-Check (Board-Style)